South African Patent No. 2002/4083 describes and claims line administration apparatus that, in effect automates the normally manual process of barring and unbarring telephone lines as a means, primarily, of reducing so-called"clip-on fraud"in which a perpetrator clips a telephone instrument onto an un-barred line and makes unauthorised calls at the expense of the subscriber in respect of that line.

This invention seeks to incorporate line maintenance and testing functionality into the line administration apparatus of South African Patent No. 2002/4083.

Summary of the invention This invention provides a method of administering communications on a line extending between administration and user equipment, the method comprising the steps of: barring the line against the transmission of unauthorised communication; monitoring the line for the initiation of communication from the user equipment end of the line ; seizing the line on the initiation of such communication;

automatically transmitting an authorisation code from the user equipment end of the line to the administration equipment; determining, within the administration equipment, whether or not the authorisation code that is valid for the user equipment; releasing the line for communication if the received authorisation code is valid for the user equipment; and periodically changing the user equipment authorisation code by transmitting a different user equipment authorisation code to the user equipment from a point remotely of the user equipment.

The method of administering communications on a line relies on conventional means of seizing and releasing a communications line such that no communication is possible on the line when seized and communication is only possible once the line has been released for communication.

Within the administration equipment, the authorisation code received is compared with the administration equipment records in respect of the user equipment to determine whether or not the authorisation code is valid for that user equipment.

The periodicity of the changes made to the authorisation code of a particular item of user equipment may vary from nil to frequent. So, for instance, the authorisation code could require changing only when an operator determines that the authorisation code for that piece of user equipment may have been compromised. In this example, the user equipment authorisation code will be changed to counter any possible breach of the security of the user equipment authorisation code, but if no such breach occurs, then no change will be necessary.

Alternatively, the user equipment authorisation code could be changed more frequently, whether manually or automatically.

The system described and claimed in South African Patent No. 2002/4083 lends itself to the use of code hopping techniques in which the user equipment authorisation codes are changed with the use of an encryption algorithm embedded in the user equipment. The user equipment authorisation code changes automatically from time to time, for instance, each time the user equipment is used and the keys used to generate the changing user equipment authorisation codes are duplicated or regenerated in the administration equipment to enable the administration equipment to determine whether or not the changing authorisation codes are valid for the user equipment concerned.

The method of this invention lends itself to use with such code hopping techniques in that the method may include the step of periodically transmitting a different user equipment authorisation code generating key to the user equipment and the administration equipment.

In each case, the user equipment authorisation codes are changed from a point or site remotely of the item of user equipment concerned. To this end, the remote site may be situated in the administration equipment, but this is not necessary and the remote site could be located remotely of both the user equipment and the administration equipment, thereby further enhancing the security of the system.

The invention includes apparatus for the administration of communications on a line extending between administration and user equipment, the apparatus comprising: means to bar the line against the transmission of unauthorised communication; means to monitor the line for the initiation of communication from the user equipment end of the line ; means to seize the tine on the initiation of such communication; means automatically to transmit an authorisation code from the user equipment end of the line to the administration equipment;

means to determine, within the administration equipment, whether or not the authorisation code that is valid for the user equipment; means to release the line for communication if the received authorisation code is valid for the user equipment; and means located remotely of the user equipment that is adapted periodically to change the user equipment authorisation code by transmitting a different user equipment authorisation code to the user equipment.

The apparatus of this invention may be adapted for use with code hopping systems by the inclusion of means adapted periodically to transmit a different user equipment authorisation code generating key to the user equipment and the administration equipment.

The means to change the user equipment authorisation codes may be situated in the administration equipment, but in an alternative form of the invention the code changing means may be located remotely of both the user equipment and the administration equipment.

The communication line may conveniently be constituted by a physical line or cable normally intended for the transmission of communication signals. The invention is, however, intended to extend to a communication line constituted by a communication channel other than a physical line, such as, for instance, a radio frequency communication channel extending terrestrially, between terrestrial-and satellite-based communication equipment or both.

In the preferred form of the invention, the apparatus is intended for the administration of communications on a telecommunication line, the administration equipment being located at a telephone exchange and the user equipment being constituted by a code transmission device or module located in or near a telephone set.

In the event that the telephone set is a normal domestic or office telephone (not a pay phone), the code transmission module may be provided as a plug-in facility adapted for

location closely adjacent the telephone.

In the event, however, that the telephone is a pay phone, the code transmission module may be located within the housing in which the pay phone apparatus is normally secured.

In this way, the pay phone and the line extending between the pay phone and the exchange may be protected against fraudulent use.

In use in a telecommunications network, the code transmission module may be used to perform a number of functions other than simply transmitting authorisation codes to. the administration equipment in the exchange and the method and apparatus of the invention are intended to incorporate such additions.

To this end, the administration equipment may be adapted periodically to transmit a test code to the code transmission module, which is adapted to switch to a test mode on receipt of the test code, in which test mode the code transmission module is adapted to receive one. or more test signals transmitted to the code transmission module from the administration equipment, to perform the test associated with each test signal and to transmit the results of the test to the administration equipment.

Examples of these tests will be described in greater detail below.

Brief description of the drawings The invention will be further described with reference to the accompanying drawings which is a block diagram of a code transmission module according to the invention.

Description of embodiments of the invention With the advent of digital telephone exchanges, a number of telephone service providers have been able to provide digital telephone line barring facilities.

The existing line barring facility is incorporated in the equipment at the exchange. Using such a facility, the line is normally barred and the line barring facility interrogates the normally barred line for an authorisation code when a communication is initiated by a user using user equipment such as a compatible telephone instrument. To unbar the line, the telephone user is then required to enter the correct authorisation code by means of the telephone keypad.

This normally requires a code that is correct for that line and the user equipment connected to that line. The line will then only be unbarred and released for communication on receipt, by the exchange equipment, of an authorisation code valid for that line and the user equipment concerned.

In the process of unbarring a line, the exchange equipment is adapted to detect the change in line current that occurs when the telephone handset is lifted and to await the receipt of the authorisation code which will normally be transmitted as a series of Dual Tone Multi Frequency (DTMF) tones from the telephone to the exchange.

?' On receipt of the appropriate authorisation code, the exchange equipment unbars the line.

When the telephone handset is replaced, the exchange equipment detects the change in line current and automatically bars the line once again.

The code transmission module 10 forming part of the administration apparatus described and claimed in South African Patent No. 2002/4083 is illustrated in the drawing. The code transmission module 10 is adapted for location closely adjacent a telephone instrument 12 and is interposed in the telephone line 14 between the telephone instrument 12 and the telephone exchange 15 (not shown) by way of telephone jacks 28 and 30.

It is also possible to integrate the code transmission module 10 in the instrument circuitry.

A current sensor 16 is used to detect the change in line current that occurs when the telephone handset (not shown) is lifted off the handset cradle (indicated by a normally open

switch 18).

A processor unit 20 is programmed to seize the line 14 when the current sensor 16 detects current on the line 14 indicating that the handset has been lifted off the cradle 18. The line is seized by means of a line seizing mechanism 22.

Within the system described in South African Patent No. 2002/4083, once the line has been seized, the processor 20 activates a DTMF interface 24 that transmits a valid authorisation code, as a DTMF tone signal, to the exchange 15 by way of the line 14.

When, at the end of the call, the handset is replaced on the cradle 18, the current sensor 16 senses the change in line current. In consequence, the processor seizes the line by means of the line seizing mechanism 22 and transmits a barring code down the line 14 by means of the DTMF interface 24. On receipt of the barring code, the line barring facility 17 in the exchange 15 bars the line against further use, thereby returning the line 14 to its normally barred state.

The code transmission module 10 is adapted for location closely adjacent the telephone instrument 12. This will ensure that that any person wishing to make unauthorised use of the line 14 must, of necessity, interrupt or clip onto the line downstream of the code transmission module 10, that is between the exchange 15 and the code transmission module 10. However, at any point between the exchange 15 and the code transmission module 10, the line 14 will have been secured, since a person clipping onto the line 14 will be met with a normally barred line and to unbar the line 14, it will of course be necessary to know and transmit the authorisation code down the line 14.

In order to further minimise the possibility of fraudulent use, the code transmission module 10 may be provided with a code hopping facilities, a code encryption technique adapted periodically to generate a different code, for instance, each time the telephone 12 is used.

The tine barring facility 17 at the exchange 15 will be provided with suitable decryption facilities. In this way, the line 14 can be secured against replay attacks-attempted fraudulent use of the line 14 in which a person tapping or listening in on the line 14 records the unbarring code and then replays or retransmits the code information to the exchange 15.

In a developed form of the invention of South African Patent No. 2002/4083, the system may be used to secure pay phones.

This invention, which relates to an improvement in the invention described and claimed in South African Patent No. 2002/4083 makes use of the code transmission module described above and provides additional functionality by the provision of a control centre 100 located remotely of the code transmission module 10.

In use, the system of this invention can be used to administer communications on the network of which the line 14 forms a part by maintaining all the lines 14 in a state in which the lines 14 are barred against the transmission of normal communication on the lines 14.

Each code transmission module 10 is then used to monitor its line 14 for the initiation of communication from the user handset situated at the code transmission module 10 end of the line, the current sensor 16 being used to detect the change in line current that occurs when the telephone handset is lifted off the handset cradle (indicated by a normally open switch 18). The line is then seized by means of a line seizing mechanism 22, in the manner described above and the code transmission module 10 then automatically transmits its pre- programmed authorisation code to the exchange 15 serving the code transmission module 10.

Within the exchange 15 serving the code transmission module 10, the authorisation code so transmitted is compared with the exchange's records in respect of the code transmission module 10 to determine whether or not the authorisation code is valid for that code transmission module 10 and its associated user equipment or handset. If it is, the line is released for normal communication.

The control centre 100-is connected to the network of which the line 14 forms a part and different authorisation codes can be transmitted periodically to one or more of the code transmission modules 10 on the network using transmission equipment 102 located at the control centre 100.

The control centre 100 can be situated at the exchange 15 or exchanges serving the network of which the line 14 forms a part, but this is not necessary.

In fact, it might be better for the control centre 100 to be located remotely of both the code transmission modules 10 on the network and the exchange or exchanges serving the code transmission modules 10, since this will further enhance the security of the system.

The periodicity of the changes made to the authorisation codes of the code transmission modules 10 on the network may vary from no changes in a given period of time to frequent changes within that period, depending on the security regime required by the network operator.

So, for instance, the code transmission module authorisation codes could be kept constant and changed only when the operator determines that the authorisation code for a particular piece of user equipment may have been compromised. In this example, the code transmission module authorisation code will be changed to counter any possible breach of the security of the user equipment or the authorisation code, but if no such breach occurs, then. no change will be necessary.

Alternatively, the code transmission module authorisation code could be changed more frequently, preferably automatically by means of a predetermined programme of code changes initiated from the control centre 100. This code changing programme does not require code hopping and is simply a method of ensuring that the code transmission modules 10 on the network have their authorisation codes updated regularly.

Where code hopping techniques are used, however, each of the code transmission modules 10 on the network will be programmed with a key that is used within the code hopping encryption algorithm so that, in use, the authorisation codes of the code transmission modules 10 oh the network change automatically from time to time, for instance, each time the user equipment associated with a code transmission module 10 is used.

The keys used to generate the changing code transmission module authorisation codes

are duplicated or regenerated in the exchange serving each code transmission module 10 to enable the exchange equipment to determine whether or not the changing authorisation codes are valid for each of the code transmission modules 10 on the network.

The method of this invention lends itself to use with such code hopping techniques in that the control centre 100 can now be used to periodically transmit a different key to one or all of the code transmission modules 10 on the network.

At the same time, the control centre 100 will transmit duplicate or complementary keys to the exchange serving the code transmission modules concerned, thereby providing complementary keys to the barring facility 17 at the exchange 15 to enable synchronisation of the code transmission modules 10 on the network with the barring facility 17.

In a telecommunications network, such as that described immediately above, the code transmission module may be used to perform a number of functions other than simply transmitting authorisation codes to exchange serving the code transmission module 10.

The code transmission modules 10 on the network are located at the end of the lines 14 associated therewith and the code transmission modules 10 are capable of communication with the exchange 15 and the control centre 100. This enables the network operator to monitor, test and undertake a number of maintenance functions on the entire line 14 associated with each code transmission module 10 and its associated subscriber equipment.

By programming the code transmission module 10 to receive, recognise and respond to one or more test codes transmitted either from the exchange serving the code transmission module 10 or the control centre 100, the code transmission module 10 can be used to perform useful remote administration of the network.

As an example, the code transmission module 10 can be programmed to switch to a general test mode on receipt of a general test code transmitted to the code transmission module 10 by the network operator, either from the exchange serving the code transmission module 10 or from the control centre 100.

The code transmission module 10 can then be programmed to receive and respond to a number of specific test signals.

Once in test mode, the network operator can, for instance, cycle the code transmission module 10 through one or more tests by transmitting an appropriate test code to the code transmission module 10.

For instance, the code transmission module 10 can, on receipt of the appropriate code, test for: OFF HOOK SIGNAL-simulate closing of the handset switch 18, which will allow the exchange serving the code transmission module 10 to test the line Voltage; ON HOOK SIGNAL-simulate re-opening of the handset switch 18, which will allow the exchange serving the code transmission module 10 to test the line Voltage ; DC LOOP CURRENT-OFF HOOK SIGNAL-simulate closing of the handset switch 18, which will allow the exchange serving the code transmission module 10 to test the line current; DIALTONE LEVEL-monitor dial tone signal received from the exchange serving the code transmission module 10 and report if not compliant with the network operator's specifications (e. g. 400Hz modulated by 40Hz-in South Africa); TONE RECEPTION AT VARIOUS FREQUENCIES-monitor tone signals transmitted by the exchange serving the code transmission module 10 at a number of frequencies (for instance, a predetermined number of fixed frequencies between 400Hz and 3500Hz, stepping up at predetermined multiples) and report if reception fails to comply with the network operator's specifications (e. g. within 30db of signal as transmitted by the exchange)-a particularly important test for data and fax lines that rely on modem communication; AVERAGE LINE NOISE LEVEL-monitor noise level on the line and report if not

compliant with the network operator's specifications SIDETONE LEVEL-monitor for impedance mismatch and report if not compliant with the network operator's specifications-a particularly important test for data and fax lines that rely on modem communication.

It will be appreciated that these examples are not intended to limit the invention to specifics but are given purely for the purpose of illustrating the functionality of the code transmission module 10.

In telecommunications networks generally, the maintenance of the network and the lines forming part of the network are the responsibility of the network operator. With the functionality of this invention programmed into the code transmission module 10, it is possible for the network operator to determine whether or not there are any faults on the line 14 that might fall within its ambit of responsibility.

The tests described above as well as similar line tests, are made possible with the code transmission module 10 of this invention since the code transmission module 10 is located at the end of the line and it is capable of communication with the exchange serving the code transmission module 10 and the control centre 100, thereby enabling a network operator to discharge its network and line maintenance responsibilities remotely.