An exchange for telecommunications, a switch and switch board therefore, and a method of switching

The present invention relates to an exchange for telecommunications, in particular to an automatic main distribution frame apparatus used in such an exchange. The invention also relates to a switch in particular a switch used in an exchange for telecommunications, in particular used in an automatic (main) distribution frame. The invention also relates to switch boards. Further the invention relates to a method of switching in an exchange used in telecommunication. An automatic distribution frame (ADF) is used to connect all operator's equipment to the cable plant. The position of an ADF is shown in figure 1. The ADF 200 is an exchange that connects equipment 201 with the cable plant 202. The ADF is an example of a switching network 200. The equipment 201 can be equipment to be connected to the network, including but not limited to voice equipment, broadband equipment, test equipment.

The amount of cables connected to an ADF apparatus varies greatly - from the big downtown exchanges with thousands of subscribers to small neighbourhood / small business exchanges with the tens of subscribes. The ADF apparatus should be highly scalable allowing addition/removal of input/output stages to fit the actual need. Wide deployment of the modern broadband technologies today also have changed the signals that must be switched by ADF, for example today's signals that flow through automatic distribution frames have a bandwidth from 0 to 100 MHz and currents from 0 to 150 mA. Broadband technologies also put new requirements on ADF, such as much faster and uninterrupted switching. The requirements for ADF are steamed from (a) compliance to telecom equipment regulations and (b) signal preservation during switching. ADF implemented using blocking or not blocking multistage architecture such as Clos. All the equipment ports are connected to the input stages of the ADF and all the output ports are connected to the cable. The flow chart is shown on figure 2. All blocks shown could be itself multistage. The embodiment shown on figure 2 is an example of an electronic switching system. A signal enters the ADF 200 at an input stage 210. In this embodiment five subscriber lines 211-215 are shown. The second line 212 is to be

connected with a first line 216 of cable 202. The thick line in Figure 2 shows the connection as arranged by the ADF 200.

The second line 212 is connected to the input stage 210. The input stage 210 is controlled by a controller 205 such that the second line 212 is connected to the third connection 217 between input stage 210 and switch stage 220. Controller 205 'chooses' this third connection 217 because it was 'free' or available to make the connection.

In the switching stage 220 the switches are arranged in such a way that a connection is made between third connection 217 and fourth connection 218 in between switch stage 220 and output stage 221. At the output stage the switches are arranged to connect its fourth input to its first output being the first line 216 of the cable 202.

Several proposals for switching in such an exchange for telecommunications are known. For example, the company Nexans ® offers several solutions for switching using a robotic hand. US 6,295,483 shows an example.

An automatic main distribution frame (ADF) apparatus can have robots automatically performing wiring or modify the combination of wires, such that every time a new subscriber wants to subscribe to an unattended telephone office, a new wiring and a modification in the combinations of wires can be automatically made. FIG.3 shows a configuration of a first conventional ADF. In the configuration shown in FIG.3, a multi-layered printed wiring board in which wires are embedded horizontally and vertically, and at the points where wires cross, holes are opened, is made a basic unit of one switch. This basic unit of a switch is called a matrix board (MB). In this configuration, a number of matrix boards 121 are arrayed and mounted on both sides of the ADF, and inside the ADF robots 123 are provided to insert a pin in the hole of the matrix board 121 for short-circuiting wires. The robot 123 determines the rough position of the point by both a row sensor and a column sensor, and locates the precise position by applying a laser beam to a reference marker provided on the surface of the matrix board 121. When finding a position to insert a pin in this way, the robot 123 inserts the pin in the hole of the matrix board 121. On the matrix board 121 a wiring pattern is formed, and wires cross with each other at the position of each hole. Therefore, when a pin for short-circuiting the wires is inserted by the robot 123, different wires are connected and a signal route is formed. By changing the position of

inserting a pin, the connecting relation between the wires is modified, and a different signal route is formed. In this way, a signal coming from the telephone cable of a subscriber is switched over in the ADF and inputted to an exchange located in a subsequent stage. In the configuration shown in FIG.3, since matrix boards 121 are provided on both sides of the ADF, robots 123 inside the ADF handle the matrix boards on both sides of the ADF.

Prior art ADFs adopt a three-stage switching configuration. If a signal route is switched over by a switch in a first stage, a signal is inputted to a switch in a second stage, and if the route is switched over again by a switch in the second stage, the signal is inputted to a switch in a third stage, and the signal outputted from the switch in the third stage is inputted to an exchange. As described earlier, when a new subscriber is accommodated in an exchange by laying a new piece of cable at the time of a new subscription or a relocation, an ADF is used to appropriately set up the signal route of the new subscriber and to accommodate the subscriber in the exchange. Although the change-over of a wiring route by a robot 123 does not occur so often and a high-speed change-over is not always required to rapidly switch over a wiring route, it is desirable that the change-over speed of the robot 123 is high.

FIG. 4 explains the connecting operation of wiring by inserting a pin in a hole of a matrix board using a robot. As shown on the right of FIG. 4, wiring is made on the hashed part of the matrix board. Wires are embedded in four layers inside the matrix board. Usually, wires are laid in both X-axis and Y-axis directions. At an intersection of the wires in both directions, a hole with a diameter of approximately 1 mm as shown on the left of FIG. 4 is made to cut a connection. Each of the output lines of the wires in the x-axis direction and in the y-axis direction are connected with another board or to an external cable through a connector unit (CN unit). The left side of FIG. 4 shows how wires embedded in a matrix board are connected by a connection pin inserted by a robot, and is a cross section of the matrix board. As shown in FIG. 4, generally speaking, wires are laid in four layers, which are classified into two groups of A and B wire layers. These A and B wires layers correspond to the upward and downward lines of a telephone circuit. For example, if the A wire is upward line, the B wire is a downward line. The X and Y layers of each of the A and B wires correspond to the wires in the x-axis and y-axis directions shown on the right of FIG. 4. The connection pin is provided with a contact spring in the middle. When the connection

pin is inserted in a hole, the X and Y layers are short-circuited, and a signal flows from an X layer to a Y layer or vice versa. Such a contact spring is provided for each of both A and B wire layers, for example, in such a way that if the upward line is connected, the downward line may also be connected simultaneously. Generally speaking, although the connection pin is made of engineering plastic, the material is not necessarily limited to engineering plastic. The material of the contact spring is not also limited to a specific material, only one that has a sufficient electrical conductivity.

FIG. 5 shows a configuration of a matrix board in a second conventional ADF. In the configuration shown in FIG. 5, the size of the ADF is reduced by locating matrix boards 140-1 through 140-4 and matrix boards 141-1 through 141-4 orthogonally to each other. The matrix boards 140-1 through 140-4 are located in parallel, and robots are provided between the matrix boards 140-1 through 140-4 to make the robots perform switching. The matrix boards 141-1 through 141-4 are also located in parallel and robots are provided between them. The matrix boards 140-1 through 140-4 and 141-1 through 141-4 are located orthogonally to each other, and are wired and connected at contacting points 142-1 through 142-4. When the matrix boards are located in this way, as shown in FIG. 3, space can be used more effectively than when all the matrix boards are located only horizontally, and the volume occupied by the matrix boards can be reduced. As a result, the volume of the ADF itself can be reduced.

FIG. 6 shows a configuration of a third conventional ADF. In the configuration shown in FIG. 6, matrix board units 154 in which a plurality of matrix boards are accommodated, are mounted on shelves, which are accommodated in a frame 150 of an ADF 149. A robot 152 is composed of a support member consisting of an elevator 152c and an arm element 152b, and a head element 152a held by this support member. The head element 152a can move back and forth along the arm element 152b, and can also move to an arbitrary position in the matrix board unit 154 in conjunction with the left and right movement of the arm element 152b along the elevator 152c. When the robot is moved to another matrix board unit 154 to perform switching, the arm element 152b is moved to either of the left and right ends of the elevator 152c, and then the elevator 152c is moved up and down the frame 150. When the robot 152 comes to the target matrix board unit 154, the arm element 152bis moved

laterally to a hole where the switching is to be performed. Such operations are controlled by a control circuit in a control package 160, and the power is supplied by a power supply unit 158. The connection (link) between the matrix board units 154 is made by providing a connector on the side of each matrix board unit 154 and using a wiring harness, etc.

FIG. 7 illustrates a further prior art embodiment showing an exploded perspective view of an exchange used for telecommunication such as an automatic wiring connection apparatus.

A large number of connections, possibly telephone lines, 172 are wired near a housing 170 which is partitioned into a plurality of small chambers by partition plates 171. Each of the small chambers stores therein a matrix board (MTB) 180 and a pin insertion and pulling out robot 190. In FIG. 7, however, in order for simplification, there is shown only the matrix board (MTB) 180 which is accommodated in one small chamber. The telephone lines 172 are to be connected to connectors, for example arranged on the left hand side of the housing 170. The lines are connected through the matrix board containing the switches with connectors at a right hand side of the housing 170, which are to be connected with the cable plant. A backplane, e.g. at the back side of the housing, is arranged to control the switches/matrix boards and is interconnecting the switching stages to I/O connectors.

The matrix board (MTB) 180 comprises a primary MTB 181, a secondary MTB 182 and a tertiary MTB 183, each of which consists of a pair of boards arranged in parallel to each other. In an embodiment according to the prior art a pin insertion and pulling out robot 190 is provided, and the pin insertion and pulling out robot 190, also accommodated in the small chamber. The pin insertion and pulling out robot 190 comprises a primary MTB-oriented robot 191, and a secondary and tertiary MTB- oriented robot 195. The primary MTB-oriented robot 191 is arranged between two boards constituting the primary MTB 181, and takes charge of insertion and pulling out of connection pins on the two boards constituting the primary MTB 181. The secondary and tertiary MTB-oriented robot 195 is arranged between two boards constituting the secondary MTB 182 and also between two boards constituting the tertiary MTB 183, and takes charge of insertion and pulling out of connection pins on a total four boards of the two boards constituting the secondary MTB 182 and the two boards constituting

the tertiary MTB 183. The primary MTB -oriented robot 191 and the secondary and ternary MTB-oriented robot 195 have pin insertion and pulling out heads 192 and 196, respectively. The pin insertion and pulling out heads 192 and 196 are vertically translated along vertical guides 193 and 197, respectively, and the vertical guides 193 and 197 are horizontally translated by horizontal guides 194 and 198, respectively, so that the pin insertion and pulling out heads 192 and 196 are translated on a two- dimensional basis along surfaces of the primary MTB 181; and the secondary MTB 182 and the tertiary MTB 183, respectively, to perform access to the primary MTB 181; and the secondary MTB 182 and the tertiary MTB 183 in connection with insertion and pulling out of connection pins .

In the automatic wiring connection apparatus shown in FIG. 7, each of the small chambers partitioned by partition plates 171 is provided with a pair of the matrix board (MTB) 180 and, according to the prior art, the pin insertion and pulling out robot 190. In the configuration according to the prior art, when a large-scale network is configure between the matrix boards of an ADF, both the required number of matrix boards and the number of holes per matrix board increase even if a three-stage switching configuration is adopted. As a result, the mounting area of matrix boards increases, and thereby the external dimensions of an ADF also increase. Furthermore, when the external dimensions of an ADF increase, the operation range of a robot also increases, which causes the following problems:

Since the structure of a robot needs to be stiffened, the robot becomes heavy and large.

While positioning in units of several tens of micrometers is required, an operation range of 1 to 2 m is needed, which is incompatible.

When the operation distance to be travelled by a robot in one operation increases, as a result, the operation time also increases.

Another solution for switching in an ADF is provided by the company Simpler Networks (http://www.simplernetworks.com). Here an ADF uses MEM propriatory technology for signal switching. MEM ADF implements highly scalable architecture and thus meets the market needs. On the side of compliance to telecom environmental conditions regulations MEM is more vulnerable than robotic hand.

It is therefore a goal of the invention to provide an improved exchange, in particular an improved automated main distribution frame that lacks at least one of the drawbacks of the prior art. It is a further goal to provide an improved switch, in particular an on/off switch. At least one of the goals is achieved with an exchange according to claim 1.

The invention provides preferably an exchange comprising an housing. The exchange could be a distribution frame, preferably the main distribution frame for telecommunication exchange. The exchange has several input and output terminals. Preferably the number of input and output terminals is equal. Each terminal is connectable to a signal carrier. The terminal can be connected to other hardware or to subscriber lines. The exchange according to the invention can be an exchange for electrical signals and/or for optical signals.

A load signal is to be transferred from an input terminal to an output terminal according to the wishes of an operator, preferably the operator of the telecommunication plant where the exchange is located.

The input terminals are connected with the output terminals through a switching network for selectively connecting a input terminal with an output terminal. The switching network allows the creation of a path, possibly multiple paths, from one or more input terminals to one or more output terminals. Preferably the switching network allows a one-on-one switching of input-output terminals.

Preferably a controller is connected to the switching network for controlling the connections to be made in the switching network. The operator can instruct the controller to change the switching network in order to configure the connections between the input and output terminals, as indicated in figure 2. A switching network according to the invention comprises at least one switch having an input that can be connected to an output. The input-output connection enables the transfer of the signal from the input to the output. The connection can have multiple states. The connection according to the invention can have a first state wherein the connection is closed, i.e. a signal is transferable. In particular the connection can be conductive in the first state. The connection also has a second state wherein the connection is open, i.e. blocking.

This connection from input to output in the switch according to the invention comprises a phase changing material, the phase changing material having at

least a first conducting state and at least a second blocking state. In the first state the material is relatively more transmissive, in particular conductive, than in the second state wherein the material is relatively less transmissive, in particular conductive. The phase changing material has at least two detectable different states. The states can differ in transmittivity, both electrical and optical as well as a combination thereof. The detectable difference is enough for the skilled person to define a relative conducting and a relative non-conducting state.

The phase changing material is capable of being switched from one detectable state to another detectable state by the application of a control. The detectable states may differ in their morphology, surface topography, relative degree of order, relative degree of disorder, electrical properties and/or optical properties and being detectable there between by the electrical conductivity, electrical resistance, optical transmissibility, optical absorption, optical reflectivity and any combination thereof. According to the invention the switch further comprises phase switch elements that are connected to the controller for switching between the at least two states. This allows an operator to change the state of the phase changing material by inputting its wishes in the controller.

The invention makes the use of the robot obsolete. Also the pin insertion and pulling out is obsolete.

Use of a phase changing material in a switch is counter intuitive. Although phase changing materials are known for a long time, use of such materials in a switch and in particular as the material being switched was not obvious because the blocking state of this kind of material is not a completely blocking state. Known blocking states of prior art switches completely block transmittivity. It is therefore counterintuitive to use a material that is not completely blocking. It is further counterintuitive to use a material as a conductor for the load current but also as conductor for a switching current. Further still the skilled man familiar with phase changing materials will suggest use of known semi-conductor materials for the construction of switches. The prior art does not suggest use of phase changing material as material for the transmitting connection in a switch.

The switching network according to the invention now comprises a switch that utilizes phase change effect in material. Under influence of a control, preferably a

control current, the material transforms from low resistance state to high resistance state.

It is known to use phase changing materials in memory elements wherein the same physical effect is used for data storage. However a major application difference here is that fact that only control currents are applied to memory element; it does not switch and there is no current flow through the memory device in "on" state.

Contrary to the MEM's, the invention provides a device having no mechanical component that can function under different environmental conditions. The solution according to the invention is less vulnerable. The solution according to the invention combines the advantages of semiconductor industry with the possibility of having a switching network that is configured in a certain state, and maintains this state even without a power supply. Power is only required to perform the switching.

Preferably the main distribution frame is arranged to electrically connect the input and output terminals through the switching network. The phase changing material has at least two states that have different conductivity, preferably a high conductivity and a low conductivity. These two states will correspond with a conducting and a blocked state respectively. The switch allows the creation of an electrical path through the ADF and switching network for transferring electrical load signals from the input terminals to the output terminals.

The controller is in a preferred embodiment electrically connected to the phase switch element. The phase switch element in this embodiment is formed by at least the input and/or output of the switch. This input and/or output of the switch has a double functionality in this embodiment. Although it is possible to configure control path separate from the switch path (through the input/output), it is possible to set a control path that could use at least a part of signal path through the switch. This further simplifies the construction of the switch, since an input or output can be connected to the switching network on the one hand and to the controller on the other hand. Again a skilled person would think of such a switch as counterintuitive, because the phase material is already used as conductor for the load current, but needs to be provided with a heating current for switching. The skilled person would not take this step, since the downstream influences of the switching current are unpredictable. The inventor however discovered that the effects are very limited.

The switch according to the invention has at least three terminals connected to at least a part of the phase changing material. The at least three terminal comprise two terminals for connecting the signal carriers, wherein the phase changing material is used for its switching properties. Two terminals are used as phase switch terminals for switching the state. The switch according to the invention has different signal paths, in particular electrical paths for load and control currents, in particular through the material's volume. Phase change effects occur between the control current terminals effectively controlling the conductivity of the path between the load current terminals.

The desired ratio of 'on' and 'off states in conductivity of the load channel is reached by selecting geometrical device parameters for the desired value of the maximum load current. If a larger load current is desired, a larger cross section (and volume) of phase changing material is used as a connection between the load current terminals. The control current or possible the heat elements are correspondingly adapted. The skilled person will be able to adapt the switch and in particular the cross section thereof to allow the desired load currents. The skilled person will recognize that the current density is an important parameter for switching the phase. The load current density should be lower than the control current density needed for switching the phase/state.

A suitable ADF is obtained according to a preferred embodiment when the switching network is arranged in at least three stages, wherein a first stage is connectable to exchange equipment, a third stage is connectable to a cable plant and a second stage is arranged for connecting the first stage to the third stage, wherein the distribution frame further comprises a control for controlling the switches. This arrangement further allows the application of a Clos-network. Such network is an example of a non-blocking switching arrangement.

It is preferred to have the switching network comprising at least a replaceable switch board with the switch mounted thereon. Such a replaceable switch board can be placed in ADFs according to the prior art.

The controller can be arranged to send a pulse signal through the phase changing material. Such a pulse signal is able to cause the phase change in the material. The pulse signal can have properties different from the 'normal' load signals in telecommunication exchanges. This could be a high current or in a different embodiment a particular frequency. The frequency could be filtered out of the output

signal of the switch if the controller is connected to the input or output in order to prevent damages or incorrect signal handling downstream of the ADF.

In an embodiment of the invention the phase switch element is a heating element. Such a heating element can be mounted near or on the switch, in particular on the connection between input and output of the switch. The heating element is preferably indirectly in contact with the phase changing material, for example a electrical insulator that is heat conducting is positioned in between the phase changing material and the heating element.

The heating element can be electrically connected to the controller. The controller can bring about a phase change by initiating the heating element. This can result in the semi-permanent crystalline structure change in the phase changing material to switch from a first to a second state or back.

In an embodiment of the invention the phase switch element comprises both an electrical connection to a controller for providing a control current for switching the phase of the phase changing material and a heating element. Use of two phase switch elements, preferably two different phase switch elements, is advantageous since specific driving pulse combinations can be used, controlled by the controller, for switching the phase of the material.

The invention also relates to a switch comprising at least an input and at least an output connected to each other through/via a connection having phase changing material, the phase changing material having at least a first conducting state wherein the material is relatively more conductive/transmissive and at least a second blocking state wherein the material is relatively less conductive/transmissive, wherein the switch further comprises at least one phase switch element connectable to a controller for switching between the at least two states. The connection can be electrical or optical. Such a switch combines the advantages known from semi-conductor industry and the semi-permanent switching without the need of a power supply. If a phase change is ordered, the phase changing material will hold the new state even in the later absence of a power source. This increases the durability and possible applications of the switch. The phase changing material can block or transfer signals of different properties. In an embodiment the switch is arranged for the transfer of optical signals. In an embodiment the switch according to the invention is used for both optical and electrical signals. The phase changing material is then able to switch from a more

transparent to a less transparent state in order to switch from on-state to an off-state. 'Transmissive' and 'blocking' according to the invention is directed at optical, electric or a combination.

It is preferred to have an electrical switch for a load current from input to output. The phase changing material has two states of more conductivity and less conductivity. This state of low conductivity is the blocking state or off- state of the switch or open connection. The skilled person knows several phase changing materials having two states with detectable different conductivities. The invention uses this detectable difference in order to differentiate the two states of the switch. At least one phase switch element is in contact, preferably electrically connected, to the phase changing material for switching between the at least two states of the material. The phase switch element can effect a change in the phase changing material, e.g. by being in direct contact, such as electrical contact, or by being in indirect contact, such as heat contact, with the phase changing material. In an embodiment an electrical current is used by a controller to bring about the phase change in the material. Hereinafter 'current control' will refer to this type of control of the phase of the phase changing material. The electrical current for phase control could be a pulsed current, preferably satisfying the conditions shown on figure 10. Preferably the current is 0,8Amp or higher. A preferred construction is obtained when the phase switch element is formed by the input and/or the output. The input or output has a double functionality. This allows a simpler construction and will lower manufacturing costs of the switch. In another embodiment the phase switch element is a heat element. The heat element can bring about the change in phase. The heat element can be controlled externally.

It is preferred to assemble the switch by using a substrate. On the substrate a layer of phase changing material can be deposited. The phase changing material forms at least a part of a connection between the input and output of the switch.

In a further preferred embodiment a part of the layer of the phase changing material is sandwiched between the phase switch elements. The phase of the material in that part can be controlled with the phase switch elements. It is possible that the phase change switches are in direct electrical contact with the layer.

It is also preferred, possibly as a further subsequent feature of the switch according to the invention, that the phase switch element is arranged on the substrate and is enclosed by an electrical insulator layer with the phase changing material arranged on the insulator layer. The phase switch element is a heating element in this embodiment. The heat is contained and limited to that part of substrate whereupon the phase changing material is deposited.

In an embodiment the switch according to the invention comprises two separately controlled phase switch elements, such as two heating elements or two current controls, and more preferably a heating element and a current control. In particular the combined control can be more efficient for large area uniform switching. A switching process can be developed for the combined heat and current switching. In an embodiment an electrode connected to the phase changing material for current control can be uniform, patterned or be a set of 1+ sub electrodes.

Further according to the invention the phase changing material is a compound including at least one selected from the group consisting of S, Se, Te, As, Sb, Ge, Sn, In, and Ag. Preferably Ge _m Sb _n Te ₀ is used, in particular Ge ₂ Sb ₂ Te ₅ or Ge ₂ Sb ₂ Te ₄ . The phase changing material could be doped, possibly with Sn.

According to yet another aspect of the invention a switch board for an telecommunication exchange, preferably a ADF, is provided having at least one switch having the phase changing material and any combination of the features of the switch mentioned in this application. Such a switch board is can be provided to replace existing prior art switch boards in ADFs.

According to a further aspect of the invention the use of a switch wherein the phase changing material is used for creating a blocking state and a transferring state is provided. Such use in automated systems offers advantages in both construction and in functionality over longer time periods in particular under the circumstance of a power failure.

A switch according to the invention as well as the exchange according to the invention will have the beneficial property of having a build-in electrical surge protection, protecting a down- stream system from high electrical currents, as a phase changing material will, under the influence of the surge current, switch phase to a nonconducting state. The switch is designed to work with a load current. This load current does not allow the switching between the load terminals. If a surge current is present in

the upstream current and is conducted towards the switch, this surge current will act as a control current and will switch the phase changing material, in particular from a conducting state to the non-conducting state or vice versa depending on the electrical scheme used. A switch according to the invention could be used as a surge protection element, possibly as part of electrical or optical system.

Further surge protection circuits of ADF can be incorporated on the MTB, possibly as a part of the switching array.

It is a further goal of the invention to provide a method of switching a telecommunication exchange in particular an ADF. The method according to the invention comprises at least connecting a number of input terminals to output terminals through a switching network comprising at least one switch having an input and output connected to each other through a phase changing material. According to the method this phase changing material has two detectable states, wherein at least a first state is a transferring or conducting state wherein the material is relatively more conductive and at least a second blocking state wherein the material is relatively less conductive. The method further comprises switching the one switch by changing the state of the phase changing material. This new method of switching a switch solve at least one of the problems mentioned in relation to the prior art and offers a durable switch that functions under very different and possibly unpredictable and uncontrollable circumstances.

The method according to a preferred embodiment comprises the changing of the state of the phase changing material by heating the material. This heating could be embodiment by a separate heating element located in the vicinity of phase changing material, but could also be achieved by heating the phase changing material itself by subjecting it to a electric power pulse.

It will be clear that the invention can be embodied in many different ways. The skilled person will be able to further deduct embodiments from this description. The skilled person will also notice that this application is possibly directed at more than one invention since the disclosure offers more than one advantage. A divisional application directed at at least one these advantages is possible.

The invention will further be described with reference to the drawings, wherein:

Figures 1-7 show prior art arrangements.

Figure 8 shows schematically a preferred embodiment according to the invention

Figure 9 shows a switching network of switches according to the preferred embodiment,

Figure 10 shows a graph for switching the phase of a phase changing material,

Figure 11 a,b show schematically a second embodiment according to the invention, Figure 12a,b show schematically a third embodiment according to the invention,

Figure 13 shows schematically a fourth embodiment according to the invention,

Figure 14 shows a graph for a second embodiment of switching the phase changing material, and

Figure 15 shows a graph for a third embodiment for switching the phase changing material.

Although reference is made to figures 1-7 in conjunction with the prior art, it will be clear that the elements described in relation with the prior art will be applied likewise in the embodiments according to the invention. An ADF according to the invention will have a similar arrangement if connected to equipment 201 and a cable plant 202. The switching stages according to prior art arrangements will be used in similar ways for the matrix board now equipped with switches using the phase change effect for switching.

An ADF matrix board (MB) with switches according to the invention is a base build up unit for exchange functioning according invention, in particular an ADF according to the invention. It contains (number of) array(s) of switches with phase changing material. The matrix board is arranged for routing to input/output/control connectors.

In an embodiment identical MB's can be used in any stage of multistage ADF according to figure 7. The implementation of non blocking connection is done on backplane. The ADF according to the invention is an electronic apparatus and as such

is not concerned with vertical/horizontal positioning of MB or number of arrays per MB or number of MB per system. The skilled person can come up with number of physical arrangements of MB per ADF.

ADF non blocking architecture is implemented by using 3 stage switching (each of the stages might be multistage). For truly non blocking architecture it is currently necessary that the number of switching arrays in every stage is identical.

A preferred embodiment of a switch according to the invention is shown in Figure 8. The embodiments shows a substrate 1. On the substrate 1 two layers 2,3 are deposited. This creates a first terminal 2 used as input, a second terminal 3 used as output. In this embodiment a layer 5 of phase changing material is deposited over the substrate 1 and layers 2,3. Thereafter a subsequent layer 4 of material is deposited over the phase changing material 5 at the same position as the output terminal 3. The phase changing material 5 forms a connection between the terminals 2,3 forming an input and output of the switch. In this embodiment terminal 2 can be connected to a incoming signal wire.

It could be an electrical signal carrier or an optical signal carrier. The material of the terminal could be an electric conductive material or an optical transmissive material. Figure 8 shows the arrangement for an electric switch. A skilled person will be able to make adaptations in order to have a more optimised optical connection wherein the loss of optical energy is reduced.

Terminal 3 is similar to terminal 2 and is connected with further equipment downstream. The further equipment could be a further switch.

Terminal 3 and terminal 4 are connectable to a controller and function as phase switch elements. These terminals are arranged to locally control the phase in the phase changing material 6. In between the terminals 3 and 4 the phase of the phase changing material 6 can be switched from a first state to a second state. This will allow changing the transmittivity of the switch.

This preferred embodiment uses one of the input/output terminals, here the output terminal as both a terminal for a load current as for a control current for switching the state of the switch. This allows the further diminishing of wires/connections necessary on the matrix board.

A first state could be a transmissive state allowing the transmission of a signal from the input through the material to the output. Preferably this is an electric

conductive state. The phase changing material has a high conductivity, in particular with respect to a second state of the phase changing material. This second state or blocking state has a lower conductivity, preferably a conductivity that is less than 3%, in particular less than 1% of the conductivity in the first state. Such a difference in conductivity is enough to create two detectably different state of the material.

The difference in conductivity is preferably in the order of 10 ³ -10 ⁴ . This will allow an effective separation of the conductive and blocking state. This is particularly effective in an ADF apparatus, wherein such switches are interconnected. The order of difference can be enlarged by enlarging the size of the phase switch elements 3,4, in particular the size of phase switch element 4. This will allow the phase changing of a larger area of the material, allowing maximizing the difference of states.

The switch dimensions (length, depth, width) are defining the maximum load and control currents through the switch as well as load path resistance in "low'V'high" state. A person skilled in the art will be able to choose the dimensions of the switch, in particular the connection between the input and output terminal using the layer of phase changing material to allow the suited load signals.

The skilled person is familiar with different phase changing materials. A suitable chemical composition is a material containing Ge _m Sb _n Te ₀ . These phase changing materials have been available. The exact chemical composition of Ge _m Sb _n Te ₀ could be used for further tune the conductive parameters of the switch.

For the ADF applications the current most preferred phase changing material has the chemical composition Ge ₂ Sb ₂ Te ₅ . This material allows the construction of a switch having a difference in electric conductive and blocking state in the order of 1000-10000.

The dimensions of the current preferred embodiment are 50 mkm in length, 20 mkm depth, and a width of 1000 mkm. The length could be in the order of 10-100 mkm; the depth could be in the order of 0.01-lmkm; the width could be in the order of 100-5000 mkm. Other dimensions are possible. The skilled person will be able to set suitable dimensions taking the load current and difference of states into account.

A particular switch according to the invention is a temperature dependent switch, which could be used as a temperature detector. The switch is in blocking state and at the room temperature; control pulses are send regulary - but these control pulses

are insufficient to heat up the material above Tcryst. If the temperature is raised to for example 100 C - the same pulse will send T>Tcrys, resulting in a phase change of the material and a switch from blocking to transmissive state. The connection opens and in this way a source could be connected to an alarm resulting in an alarm sounding. If the environmental conditions (temperature) are know and stable, the controller is programmed to bring about a heating sufficient to result in a phase change. If the controller is electrically connected to the phase changing material and sends a control pulse for switching, said control pulse can be tuned to accommodate the temperature factor. In a preferred embodiment the control pulse for ADF application will assume -70 C as default temperature. The control pulse will under any circumstance be sufficient to bring about the phase change.

While awareness of the outside temperature is not critical for an ADF application, since the ADF is arranged to function in the -70...+50 C range, it is possible to modify the system according to the invention, wherein the system includes a temperature sensor, and wherein the control current from the controller for switching the phase material is adapted in accordance with the detected temperature. The control current is e.g. 10% less if the temperature is 5OC higher.

Figure 9 shows a top view of a part of a matrix board 10, whereupon switches according to the preferred embodiment a formed. The matrix board is manufactured for switching four signal carriers 11-14 (A). The four signal carriers can be connected to the four outputs 15-18 (B) in a non-blocking fashion. This simple circuit comprises 4x4=16 switches according to the preferred embodiment. Each of these switches is connected with the four inputs and four outputs. Since the switches have a blocking and transmissive state each input can be connected with each output. To switch one of the switches, each switch is connected to a controller 8 through one of the sixteen connections (shown 4 connections). Initially input- 1 can be connected with output- 1, 2 with 2 (2-2), 3-3 and 4-4. If input 1 has to be connected to output-3, the switch connecting input- 1 with output-3 is switched from blocking state to conducting state. This switch can be identified as the third switch on the first line [1,3] on the matrix board. Now output-3 is temporarily connected to input- 1 and input-3. Switch [1,1] is in the conducting state and is controlled by a pulsed current through the phase switching elements so that the phase of the material changes and is switched to

the another state, in particular the blocking state. At the same moment the state change of switch [3,1] and [3,3] is initiated. In the end 1-3 is connected and 3-1. The order of switching can be adapted. In a preferred embodiment a diode is used in the downstream equipment. In a particular embodiment the control current flows from terminal 3 to terminal 4. This is opposite direction of the load signal. This makes separation of the two signals sharing part of the path more easy.

Figure 10 shows a graph with details with respect to switching the phase of the phase changing material. Switching to the "transmissive" state is performed by locally raising the temperature of the material above material's crystallization temperature (T cryst). Switching to the blocking state is performed by locally raising temperature of the material above the material's melting temperature (T melt). The pulse for switching to the "ON" state has a duration tl that is longer or equal to the duration for the "off" pulse t2. Back front t3 is preferably longer than back front t4.

A second embodiment of a switch according to the invention is shown in Figure 11 and comprises a substrate 20. Figure 11a illustrates a cross sectional view of a switch according to an embodiment of the invention and figure l ib illustrates a top view of the same embodiment.

On the substrate layers 22-24 are deposited. This creates a first terminal 22 used as input, a second terminal 24 used as output and a control terminal 23. In this embodiment a layer of phase changing material 21 is deposited over the substrate 20 and layers 22-24. Thereafter a subsequent layer 25 of material is deposited over the area 26 of phase changing material at the same position as the control terminal 23.

In this embodiment terminal 22 can be connected to a incoming signal wire. It could be an electrical signal carrier or an optical signal carrier. The material of the terminal could be an electric conductive material or an optical transmissive material.

Figure 10 shows the arrangement for an electric switch. A skilled person will be able to make adaptations in order to have an more optimised optical connection wherein the loss of optical energy is reduced.

Terminal 24 is similar to terminal 22 and is connected with further equipment downstream. The further equipment could be a further switch.

Terminals 23 and 25 are connectable to a controller and function as phase switch elements. These terminals are arranged to locally control the phase in the phase changing material 26. In between the terminals 23 and 25 the phase of the phase

changing material 26 can be switched from a first state to a second state. This will allow changing the transmittivity of the switch.

In Figures 11a and 1 Ib the connections to external sources are indicated. Connection A and B are connections with an input source and output connection. C and D represent connections to a control circuitry.

Figure 12 shows a third embodiment of a switch 40 according to the invention. Figure 12a is a cross section view and figure 12b is a top view of the third embodiment. Here switch 40 is created on a substrate 41. A first layer 42 is deposited on the substrate 41. This first layer 42 is preferably a heating element having two phase switch elements 43,44 at the ends thereof. The heating element is formed as a meandering layer 41, indicated by arrow 51. The ends are connectable to a controller. The controller is not shown in figure 12 but could be connected to ends C,E. The skilled person will understand that a current source or another suitable power source can be connected to the heating element 41. The controller can control the current and can control the temperature of the heating element.

The layer 41 is covered with a second layer 45 of current insulating material. This material has heat conducting properties. However the heat conduction is limited. This way only the temperature of the layer 45 is raised only locally.

The phase changing material 46 forms a third layer, deposited on top of the electric insulator 45. A separate input 47 and output 48 are formed on the phase changing material 46. The terminals A,B are connectable with upstream and downstream equipment respectively. A load current can flow from terminal 47 to terminal 48 if the phase changing material is conductive.

If the phase of the phase changing material is switched from conductive to blocking, preferably by raising the temperature of that material locally to above the melting temperature under influence of the heating element 41 controlled by the controller, than the load current is blocked at the switch. This arrangement can be used on a matrix board according to the invention. The switch can be used in exchanges for telecommunication exchanges, in particular ADF's. Figure 13 shows a fourth embodiment. A substrate 70 is provided and in a method according to the invention layers 71-77 are deposited on the substrate. In the shown embodiment a first layer 71 is deposited on the substrate, layer 71 functioning as a heating element. The heating element 71 can be connected to a source, such as an

electric source, which can provide a current to heat the heating element. In an embodiment the temperature of the heating element 71 can be controlled. Part of the layer 71 is covered with an electric insulator 72 that can conduct heat. On the insulator 72 a third layer 73 is deposited which is surrounded with phase changing material 74. Third layer 73 is connected to a controller (not shown) and forms a control path electrode 73. The control path electrode is arranged and constructed as a phase switch element for changing the phase of layer 74 formed by phase change material. On top of layer 74 input and output terminals 75,76 are formed as well as a second control path electrode 77. Electrodes 73,77 together allow the use of a control current to be conducted through phase changing material 74 in order to change the phase of the material. This fourth embodiment is provided with two independent phase switch elements for switching the phase of layer 74. This allows a large area uniform switching.

Figure 14 shows an example of a switching process illustrated in a time graph showing the temperature in the phase changing material as a result of control pulses in the phase switch elements formed by heating layer 71 and electrodes 73,77. In a left hand side of figure 14 a possible switching to a low resistance state is illustrated. The heating element 71 is provided with a control current from a controller to bring the heating element 71 and the phase changing material 74 to a temperature 83 between Tcryst and Tmelt. A further electrical pulse, resulting in a limited temperature rise 85, is sent a period tlO after starting the heating of element 71 to electrode 73,77 to facilitate switching especially of the phase changing material in the direct vicinity of the electrodes 73,77.

The right hand side of figure 14 shows switching the phase changing material layer 74 to a high resistance state. According to the method the heating element 71 is controlled to obtain a temperature 84 close to the Tcryst of the phase changing material 74. After a period, an electrical control pulse is sent through the phase changing material using the second phase switch elements 73,77 to bring the temperature of the material above Tmelt and effect a phase change, switching the phase. In this method the electrical control pulse resulting in the temperature rise 86 is aligned and synchronised with a heater control pulse in order to allow the temperature to drop quickly under Tcryst, as shown in figure 14. A skilled man will understand that figure 14 is only a schematic representation of the temperature in the phase changing

material. Such switching is preferred for embodiments of a switch having an area in excess of 250 nm2. Figure 15 shows a further embodiment of a method for switching the phase changing material, in particular for switching to the 'off state. In order to obtain a high resistance uniformly throughout at least a larger part of layer 74 according to the fourth embodiment, the heating element 71 is controlled, indicated by dashed line 88, to obtain a temperature below Tcryst during a first period tl 1. In an embodiment the heating element is pulsed. In an embodiment the heating can be continuous. The heating element is arranged and constructed to heat the whole volume. A short delay after starting to raise the temperature of the heating element 71 a electric control pulse is sent to phase switch element 73,77, indicated by dashed line 89, to bring the temperature above Tmelt. Almost simultaneously both control currents are terminated allowing the fall of the temperature of the phase changing material 74 under Tcryst, as indicated with arrow 91. In a preferred embodiment, almost directly when the temperature drops under Tcryst, the cycle is repeated. In an embodiment the current for heating the heating element 71 is already provided before the temperature has dropped under Tcryst. Due to its nature, heat conduction is relatively slow. The repeat of the cycle will result in bringing the temperature of the phase changing material above Tmelt, again using the combined effect of the heating and electrical control current. The cycle can be repeated a third or more times. This patent application or subsequent divisional applications also concerns the use of a switch having a load channel comprising phase changing material, as a surge protection. A surge current will bring the phase changing material in a non- transmissive state, blocking subsequent currents to downstream equipment, thereby protecting the equipment. In this embodiment the terminal for the surge current can be the input terminal. No additional phase switching terminal is needed for switching to the blocked state. However a switching terminal can be present for switching from blocking to non-blocking. The switch can comprise any of the embodiments indicated in this application.