COMMUNICATION SYSTEM

BACKGROUND OF THE INVENTION

There are a large number of small businesses and small organizations which typically employ only a few people. These small businesses or organizations, which are often run from homes or rented office space, generally require a commumcation system which provides access to the switched public telephone network and additionally allows for internal communication between various persons situated in various locations throughout the organization's premises. To date, there are very few, if any, communication systems which are of sufficiently low cost to be effectively utilized by small organizations or the small or home based business office.

Currently, products designed to meet the needs of small business include intercom systems and small private branch exchange (PBX) systems. Intercom systems require a separate wiring network throughout the organization's entire premises that is typically independent of the telephone wiring network throughout the premises. Additionally, intercom

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system systems usually require the purchase of independent intercom units. Moreover, installation of intercom systems is usually rigid and does not provide much flexibility for future expansion. In particular, most of these systems do not connect to the premise's existing phone line and hence do not offer enhancements to standard telephone units. Furthermore, most intercom systems require installation by a professional installer, hence the typical installation cost is quite high.

PBX systems typically employ a separate line to each telephone extension and provide, at a relatively high cost, a plurality of switching mechanisms to interconnect the separate lines, thereby providing privacy of communication between extensions while allowing any extension private access to the public telephone network. However, a common inconvenience in such systems resides in the need by the user to dial a special code typically required for each function provided, such as accessing an extemal line. To overcome the inconvenience, manufacturers generally offer special "smart" phones at a high price with dedicated buttons for each such function. Additionally, most systems of this kind do not operate during a power failure, thus denying use of the public telephone network for most of the extensions at that time. More importantly, the high costs of such systems usually excludes their use by the average domestic consumer or small organization.

SUMMARY OF THE INVENTION

The present invention provides a communication system designed to provide a convenient and effective solution to the needs of the small organization or the average home. Towards this end, the communica¬ tion system of the present invention is capable of utilizing the pre-existing standard tone or rotary telephone units and the conventional telephone wiring network of typical buildings.

The communication system of the present invention includes a central controller, connected to, and for control of, an extemal telephone line, an intemal telephone line and an intemal signal line; a plurality of telephone stations, each comprising a telephone and a signalling device connected, in parallel, to the intemal telephone line and the signal line, respectively, wherein the signalling device is operative to transmit a request signal over the signal line to other such devices in the system and operative to transmit over the signal line a command signal to the central controller for either connecting the intemal telephone line to the extemal telephone line or disconnecting the two lines thereby allowing only intemal communi¬ cation between the telephones associated with various stations.

The system preferably utilizes a premises' existing telephone wiring and priorly purchased telephone devices and thus, the installation of the system is comparably fast and easy. In view of its simple construction, the cost of the system is relatively low compared to intercom or PBX systems. Overall, the system of the invention is readily affordable by the average home owner and/or small office.

In accordance with a preferred embodiment of the present invention, the communication system has the following features: direct access to an extemal line when a telephone handset at station is lifted, a hold function in the central controller for putting an extemal caller on hold while allowing intercom-like communication between telephones of various stations, an extended hold function to allow placement of a handset at a first station and resumption of the call at a second station, an indicator on each signalling device which indicates when an extemal telephone line is used and when an extemal call is on hold, e.g. an indicator light which is lit continuously when the extemal telephone line is in use and which flashes in the hold mode.

Optionally, the system of the present invention comprises a door station, which station includes a door intercom unit for interfacing the intemal telephone and signal lines with a door latch which unlocks a door in response to an appropriate command signal from any of the signalling devices, and with an intercom panel which enables voice communication with any telephone. The door intercom unit also includes a ringer means for alerting persons preferably via all signalling extensions about the presence of an individual outside the premises and is capable of transmitting appropriate signals in respect thereof over the signal line. In the communication system of the present invention, communication between the central controller and the signalling devices, and between these devices themselves, occurs along the dedicated signal line. The majority of existing homes and offices have existing telephone wiring which contains four wires within the same cable sheath, two of which, namely the Ring and Tip wires, are used for interfacing with the public telephone network, while the other two wires are typically unused and hence can be utilized in accordance with the present invention as the signal line.

Communication between the central controller and the signalling devices utilizes a pre-determined communications protocol. Towards this end, each system unit within the communications system, including the central controller, signalling devices and other optional units such as the door intercom unit, have a unique address in order to enable communication to a particular unit. The protocol also supports a broadcast communications mode, wherein all system units can be simultaneously accessed.

The central controller preferably comprises a logic processor, message means associated with the processor for transmitting a command over the signal line to a given system unit, switching means controlled by the processor for connecting the extemal line to the intemal line so that a

given telephone may communicate with the extemal public telecommuni¬ cations network, a holding circuit controlled by the processor for putting the extemal line and/or intemal line on hold, and an intercom means controlled by the processor for allowing telecommunication over the intemal line with the extemal line disconnected.

Each signalling device preferably comprises a keypad of dedicated keys for accepting a user's requests. This device further comprises a logic processor, message means associated with the processor for transmitting a command over the signal line to other system units and means for indicating when the signalling unit is being signalled.

Communication between telephone extensions, i.e. in an intercom mode, is effectuated over the intemal telephone line. As only one intemal telephone line is utilized in the communication system of the present invention, the system cost is kept relatively low compared to PBX systems, however there is no privacy of conversation between telephone extensions thus a third telephone extension may participate in the conversation between the aforementioned two telephone extensions.

BRIEF DESCRIPTION OF THE DRAWINGS For better understanding the invention will now be described, by way of example only, with reference to the annexed drawings in which: Fig. 1 is a schematic representation of a communication system in accordance with a preferred embodiment of the present invention;

Fig. 2 is a functional block diagram of a central controller used in the system of Fig. 1;

Fig. 3 is a block diagram of a control algorithm in accordance with a preferred embodiment of the present invention for operating the central controller illustrated in Fig. 2;

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Fig. 4 is a flow chart of a main module used, in a preferred embodi¬ ment of the present invention, in the control algorithm depicted in Fig. 3;

Fig. 5 is a functional block diagram of a signalling device used in the system of Fig. 1;

Fig. 6 is a block diagram of a control algorithm in accordance with a preferred embodiment of the present invention for operating the signalling device illustrated in Fig. 5; and

Fig. 7 is a functional block diagram of a door intercom unit used in the system of Fig. 1.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Referring to Fig. 1, there is shown a schematic representation of a communication system 1 in accordance with a preferred embodiment of the present invention. A central controller 8, whose function will be described in greater detail below, is connected to an extemal phone line 2 for communication with the public telecommunications system, and is connected to an intemal signal line 4 and an intemal phone line 6 for intemal communications. Preferably, the communication system of the present invention utilizes a premises' pre-existing telephone wiring which typically comprises four wires in a single cable sheath, two of which are telephone signals, i.e. the Ring and Tip signals, and two of which are generally unused. Thus, in the present invention, intemal signal line 4 is comprised of the two, generally unused wires to constitute a transmission line, while the intemal telephone line 6 is comprised of the two wires which function as the Ring and Tip telephony signals.

The central controller 8 is connected through the signal line 4 and intemal phone line 6 to a plurality of uniquely identified stations. Each station comprises a telephone 10 and an associated signalling unit 12 or 11. The telephone 10 is preferably a standard, conventional, i.e. tone or pulse,

telephone that is typically owned by the consumer prior to purchase of additional components 8, 12 of the present invention, and connects to the intemal phone line 6, preferably using standard, commercially available modular telephone jacks and extensions thereof (not shown in Fig. 1). The telephone 10 may include a typical wireless telephone model and those models having extended features such as a dialing memory etc. The signalling unit 12 is connected, preferably using conventional modular telephone jacks, to the signal line 4 and thus associated with the said telephone 10. The function of signalling unit 12 includes transmitting a user's requests, such a Hold request, discussed infra, over the signal line 4 to central controller 8, or other system units as well as for signalling other stations and/or units of the system 1 and for indicating when the said station is being signalled.

Additionally, at least one optional door intercom unit 14 may be connected to intemal phone line 6 and intemal signal line 4 for controlling a door latch to open/lock a door 16 and for controlling an intercom panel 18 which allows persons outside of the premises to communicate by the telephone 10, in an intercom mode, with persons situated safely therein. Each signalling unit 12 or door intercom unit 14 is associated with a unique address, preferably by setting a DIP switch located on each system unit. A pre-determined communications protocol is used for communicating commands and/or requests, in a digital format, along the signal line 4. For clarity in the discussion to follow, the digital command information carried over the signal line is referred to as "messages" or "signals".

The central controller 8 supervises and controls most of the communication system 1 operations. For example, in order to effectuate a user's request, such as putting the extemal line 2 on hold, the user will

press the appropriate key on the signalling unit 12 (see Fig. 1). Control logic, i.e. software, controlling the signalling unit 12 recognizes the pressed key, interprets the desired request, e.g. through an embedded ROM look-up table, and transmits an appropriate command message utilizing the predetermined communications protocol (discussed infra) over the signal line 4 to the central controller 8. The central controller 8 receives the message, preferably sends an acknowledgement signal over the signal line 4 to the originating signalling unit 12, and carries out the desired request. The central controller 8 however, does not exclusively co- ordinate messages along signal line 4. For example, when a user at a station X requests to converse with a user at a station Y, the originating signalling unit 12 associated with station X thence transmits a request signal over the signal line addressed to the target signalling unit 12 at station Y. The message is received by all units including the central controller 8 but is only processed by the target signalling unit 12 at station Y which acknowledges the command. In this example, the target signalling unit 12 may flash an indicator light, sound a buzzer or do any other action in order to alert the intended recipient person(s).

Fig. 2 is a block diagram illustrating the central controller 8. A logic processor 20, such as any of the many commercially available microprocessors, receives a number of extemal signals including an intemal off-hook signal from an intemal off-hook detect circuit 26 as convention¬ ally known in the art per se, a ring-detect signal and an extemal-off-hook signal derived from a ring and off-hook detect circuit 24, as conventionally known in the art.

The processor 20 controls a number of components including a Receive/Transmit circuit 28 for communicating serial data along signal line 4 and a signal line power relay 31 which enables power over the signal line 4. The processor 20 also controls a hold relay 32 and a music circuit

29 for putting the extemal line 2 on Hold whilst providing music to an extemal caller. In addition, the processor 20 controls an intemal relay 33 for connecting the intemal phone line 6 to the extemal phone line 2 via the hold relay 32, or to a power supply 22 which provides a DC bias voltage on the intemal line 6 in order that it may be used internally to interconnect, in an intercom mode, telephones 10 and/or intercom panel 18. Various tones are produced over the intemal phone line 6 by means of a conventional tone injection circuit 30 as known in the art, per se, which is connected to the intemal line 6 and controlled by processor 20 to provide an audible feedback to the user as to function keys pressed or indicate an incoming extemal call while in the intercom mode.

Referring additionally to Fig. 3 there is shown a block diagram of a control algorithm 34 for operating central controller 8 (see Fig. 2). An initialization module 35 is executed when the central controller is powered- up or whenever reset conditions exist. Module 35 reads the central controller's unique address, e.g. by reading DIP switches associated with the central controller 8, and initializes the central controller's RAM and communication ports.

The control algorithm 34 is particularly responsive to handling extemally triggered events such as the reception of requests or messages from signalling units 12 or changes in the state of telephony signals such as on/off hook signals. henever a message, i.e. data bits thereof, is received by central controller 8, an extemal interrupt signal 44 is generated by an interrupt generating circuit (not shown in Fig. 2) described infra, and received by processor 20 wherein an interrupt service module 37 processes the incoming data stream and verifies incoming requests or messages. A decoding module 38 decodes the received message whereupon control is passed to one of a plurality of execution modules for executing or process-

ing the incoming message. If the received message is not addressed to the central controller 8, it is ignored and control is passed to a main module 36 whose function is described further below.

A module 41 is executed upon reception of a HOLD request from any of extensions 12 whereupon the module 41 instructs processor 20 to set (hold & int) control signals (see Fig. 2) for the hold relay 32 and intercom relay 33 in order to connect extemal line 2 to music circuit 29 and to enable, i.e. to power, the intemal line 6 for use as an intercom. A module 43 is executed upon reception of a LINE request indicating a desire for use of the extemal line 2 upon retum from a HOLD mode or while in an intercom mode. In this case, module 43 sets relays 32 and 33 to connect extemal line 2 to intemal line 6. In a similar fashion a module 42 enables the intercom upon reception of an ACK message which is received when a buzzer on the intercom panel 18 (see Fig. 1) is activated. Upon reception of a self-test command, a self-test module 40 executes self-testing diagnostics, as per conventional practice, in order to control the appropriate indicators, such as a "ready"-state LED, located on the central controller 8.

Upon termination of the execution of any of modules 39, 40, 41, 42, 43 etc., control is passed to main module 36 which monitors the state of the various telephony signals and keeps track of the reception of messages and the current mode of operation of the central controller 8. The algorithm for main module 36 is shown in Fig. 4.

When a ring detect telephony signal (see also Fig. 2) from the extemal line 2 is ascertained by main module 36, or when a station request message is perceived by decoding module 38, a tone injection module 39 operates the tone injection circuit 30 to produce a voltage on the intemal phone line 6 suitably adapted to serve as audible feedback over the handset or to alert the user through the ringing of telephone 10.

Fig. 5 is a functional block diagram of the signalling unit 12. A micro-processor 50 is connected through its data ports to a key-pad 51 for data entry, an LED 54 for indicating the state of the unit 12, a buzzer 55 for audible indication and a DIP switch 56 for denoting the unit's address. In addition, the micro-processor 50 is connected to signal line 4 via interface circuitry 52 from which power to the unit 12 is supplied from signal line 4 and an extemal interrupt signal 53 is derived from and connected to the micro-processor 50.

Preferably, the key-pad 51 includes dedicated keys (not shown in Fig. 5) including a Hold key, a Talk to intercom key 18, a Door open key, a Broadcast key for sending messages to all signalling units simulta¬ neously, as well as a dedicated key for signalling each station in the system 1.

In an alternative embodiment of the present invention, a non- volatile memory, such as an EEPROM, replaces the DIP switch 56 in each signalling unit in the preferred embodiment of the invention, and can be programmed by the user via a dedicated program key preferably included in key-pad 51.

Referring additionally to Fig. 6 there is shown a block diagram of a control algorithm 60 for the operation of signalling unit 12 (see Fig. 5) A main module 61 preferably repetitively polls key-pad 51 in order to transmit the user's request along signal line 4 to the central controller 8, other signalling units 12 or door unit 14. An encoding module 65 and a transmitting module 66 respectively encode and transmit a user's request over the signal line 4. An acknowledgement module 67 waits for an acknowledgement message from the central controller 8; if it is received within a predetermined time period the fact that the acknowledgement has been received is conveyed to the main module 61, otherwise, an error condition is conveyed to main module 61. An interrupt service module 62,

similar to module 37 of Fig. 3, receives and verifies incoming requests or messages from the central controller 8. A decoding module 63 interprets the incoming message and passes control to one of a number of execution modules. If the received message is addressed to a different unit, it is ignored and control is passed back to the main module 61. A module 64 operates buzzer 55 when the given signalling unit 12 is signalled by another signalling unit 12.

Fig. 7 is a functional block diagram of the door unit 14. Preferably, a microprocessor unit 70 is coupled, via suitable interface electronics 72, including a conventional telephone jack 71, to the signal line 4 and intemal phone line 6. In addition, the microprocessor 70 receives a ring-detect signal 73 which is active when the buzzer on intercom panel 18 is activated. The microprocessor 70 controls output signals 74 (dLatch) and 75 (spen) which, upon request, are respectively used to actuate a door latch and connect, through a speech circuit (not shown), a speaker in intercom panel 18 to intemal phone line 6. The door unit 14 is controlled by software operative to communicate with the central controller 8, similar to the algorithms presented in Figs. 3 and 6.

A wide variety of communication protocols can be used in the system of the invention so long as the protocol provides a relatively high degree of communication success rate. In the preferred system of the present invention, an originating unit transmits each message preferably five times whereby reception of two of identical messages within a predetermined time interval, say within a few hundred milliseconds, by a target unit implies a verified command for which an acknowledgement message is transmitted back to the originating unit. In the event two messages, originating from differing system units, collide on the signal line 4 thereby preventing proper decoding and acknowledgement, the originating unit 12 will generate an

error tone indicating communication failure. It will be appreciated, however, that messages in the system are scarce, thus collisions rarely occur. As only one line 4 exists for transmitting signals, the communication protocol provides for a means of embedding a clock signal in addition to data sent over the line, using for example, any of the well known synchronization methods known in the art, perse. In the protocol of the preferred embodiment of the present invention, data bits are transmitted superimposed with a stream of pulses of fixed frequency, that is, a data bit is present in the message signal a short, predetermined time after the occurrence of a pulse. Thus, an interrupt generating circuit, as mentioned supra, generates an interrupt signal for each voltage level transition present on signal line 4 so that, in conjunction with the interrupt service routines 37 or 62, the embedded data bit may be easily recovered based on bit high and low time ratios, thereby eliminating the need for an accurate clock. Referring back to Fig. 1, the communication system of the present invention includes, if desired, an added "follow me" feature which utilizes a "smart station" 11 that incorporates an automated dialer so that when the occupan,t is in a different physical location and the intercom panel 18 is activated by visitors situated outside of an organization's premises, the dialer may automatically dial a pre-programmed number and the central controller 8 may then connect by telephone the occupant at the remote location with the visitor so as to enable conversation between the two parties.

It will be appreciated by persons skilled in the art that the present invention is not limited by what has ben particularly shown and described herein. Rather, the scope of the present invention is defined only by the claims which follow.