GB2203614A

GB2203614A - Control of access to a telephone

Info

Publication number: GB2203614A
Application number: GB08708479A
Authority: GB
Inventors: John Philip Chambers
Original assignee: British Broadcasting Corp
Current assignee: British Broadcasting Corp
Priority date: 1987-04-09
Filing date: 1987-04-09
Publication date: 1988-10-19
Also published as: GB8708479D0

Abstract

To avoid the problem of nuisance telephone calls a telephone calling station (1, 5) is equipped to generate an identification signal. At the receiving station the incoming identification signal is compared with predetermined acceptable identification signals by an answering unit (3) and if the signal corresponds to an acceptance identification signal, the calling station is connected to a receiving station (4). The identification signal can be d.t.m.f. tones as from a touch-tone telephone instrument. <IMAGE>

Description

CONTROL OF ACCESS TO A TELEPHONE This invention relates to telephone systems, and in particular to controlling access to a subscribing telephone such as on a public telephone network.

In the past, there have been a number of ways of avoiding nuisance telephone calls, that is, unwanted calls from identified or unidentified callers. Incoming calls may be intercepted by the operator, or an answering machine may be installed to enable the incoming call to be heard before the called party has to speak.

More drastically all incoming calls may be barred, or the telephone number may be changed.

These options are either expensive or very inconvenient. The present invention aims to overcome these problems, and is defined in its various aspects in the appended claims, to which reference should now be made.

In a preferred embodiment of the invention the identification signal is conveniently an audible signal within the telephone width of 300-3400 Hz which may be a CCITT standard d.t.m.f.

(dual tone multi-frequency) tone pair generated by a touch-tone telephone. Alternatively, a d.t.m.f. source held to the microphone of the handset of a conventional telephone may be used on systems not equipped for touch-tone dialling.

A better understanding of the invention and its advantages may be gained from the following description of preferred embodiments thereof, given with reference to the accompanying drawings, wherein: Figure 1 is a block diagram of a first embodiment of the invention; and Figure 2 is a block diagram of an alternative embodiment.

So called 'touch-tone' telephones already use CCITT standard d.t.m.f. (dual tone multi-frequency) tone pairs which are ideal as caller identification signals. In the embodiment of Figure 1, a touch-tone telephone 1 is connected through a public switched telephone network 2 to an answering unit 3 and a receiving station 4. The receiving station is called in the usual way and the call is 'answered' by an answering unit 3, in the same way that a conventional answering machine would answer an incoming call. The caller then generates an identification signal, which may be a prearranged sequence of numbers, such as 3541, by pressing the appropriate keys of the touch-tone telephone 1. The signal is decoded by unit 3 which recognises whether the signal is accceptable, for example, by comparing it with stored acceptable signals.If the signal is acceptable, the unit 3 will connect the receiving station 4 and the telephone there will ring, whereupon the call is connected if the called party answers.

The answering unit 3-comprises a decoder 5 coupled to the network 3 which decodes the encoded identification signal. The decoder is responsive to a call from the calling station 1. Only if the decoded identification signal is acceptable, will connection to the receiving station be completed through a connector 6 coupled between the network and the receiving station.

Integrated circuits for generating and detecting tone pairs used by touch-tone telephones are in mass production. Callers on PABX equipped with touch-tone, already have the means to send such signals during a telephone call and, as exchanges become equipped to handle touch-tone 'dialling', the option will become widely available. Telephones switchable between impulse and touch-tone calling may be used to establish a call using impulse dialling and then send the signals using the touch-tone mode.

Figure 2 illustrates a system similar to that of Figure 1, except that the touch-tone telephone has been replaced by an impulse telephone 7 used in conjunction with a d.t.m.f. acoustic source 8.

The d.t.m.f. source 8-is held near the microphone of the handset of telephone 7 and the appropriate number sequence is pressed to generate the caller identification signal.

In either of the two embodiments described, the answering unit may be programmed to send a 'prompt' signal to the calling station indicating to the caller that an identification signal is required.

The prompt signal may conveniently be a single frequency tone.

The answering unit may only accept a single identification signal. Alternatively a number of identification codes may be acceptable and the unit 3 would display by means of lights or an alphanumeric display the particular identification code used by the calling party to enable that party to be identified by the receiving party before the call is taken or refused.

The system requires all calling stations to be equipped with suitable identification signal generating equipment. An access can only be gained by having suitable equipment and knowledge of the acceptable identification code or codes. The codes may be of increased length where greater security is required.

Commonly a single telephone station will contain the necessary additional components to act selectively both as a calling station or as a receiving station.

Many improvements on the basic principle described are possible and will occur to those skilled in the art. For example the answering unit 3 may be selectively disabled to allow all calls to be received by the receiving unit 4. The answering unit 3 may include a basically conventional answering machine which could record all identification signals corresponding to failed attempts.

The signals themselves could comprise numerically-coded messages sent for the called party which could be recorded without disturbing the called party. The answering unit could respond to incoming calls activating a recorded message requiring the caller to identify themselves or to confirm their own telephone number. Another alternative would be to issue a random number challenge requiring the caller respond in a way that is a known function of that number and other known variables.

Claims

CLAIMS:

1. Apparatus for controlling access to a telephone receiving station from a telephone calling station through a telephone network, comprising means associated with the calling station and coupled to the network for encoding and sending an identification signal when a call from the calling station has been connected through the network, decoding means coupled to the network and responsive to a call from the calling station to decode the identification signal, and means coupled between the network and the receiving station for completing connection of the calling station with the receiving station only if the identification signal decoded by the decoding means is acceptable.

2. Apparatus according to claim 1, wherein the identification signal comprises one or more CCITT standard d.t.m.f. tone pairs.

3. Apparatus according to claim 1 or 2, wherein the calling station is a touch-tone telephone and the identification signal is generated by the touch-tone telephone.

4. Apparatus according to claim 1 or 2, wherein the calling station is an impulse dialling telephone and the identification signal is generated by a separate tone frequency acoustic source.

5. Apparatus according to any preceding claim wherein the decoding means includes means for comparing the decoded identification signal with predetermined stored acceptable signals.

6. Apparatus according to any preceding claim wherein the decoding means includes disabling means to allow direct connection between the calling station and the receiving station.

7. Apparatus according to any preceding claim wherein the decoding means includes means for recording unacceptable received identification signals.

8. Apparatus according to any preceding claim wherein the decoding means includes means for responding to an identification signal with a prerecorded signal.

9. Apparatus according to any preceding claim comprising prompt means for prompting the identification signal from the calling station.-

10. A method of controlling access to a telephone receiving station from a telephone calling station through a telephone network, comprising the steps of encoding and sending an identification signal from the calling station to a located decoder between the public telephone network and the receiving station, decoding the identification signal at the decoder, comparing the signal with predetermined acceptable signals, and connecting the calling station to the receiving station only if the identification signal corresponds with an acceptable signal.

11. A method according to claim 10 wherein the identification signal comprises one or more CCITT standard d.t.m.f. tone pair.

12. A method according to claim 10 or 11 comprising the step of sending a prompt signal from the decoder to request the identification signal.

13. A method according to any one of claims 10 to 12 wherein the identification signal is generated from a touch tone telephone.

14. A method according to any one of claims 10 to 12 wherein the identification signal is generated by a d.t.m.f. souce acoustically coupled with an impulse dialling telephone.

15. A method according to any one of claims 10 to 14 wherein unacceptable received identification signals are recorded by the decoder.

16. A method according to any one of claims 10 to 15 wherein the identification signal is answered with a pre-recorded signal.

17. A method according to any one of claims 10 to 16 wherein the decoder is disabled to allow direct connection between the receiving and calling stations.

18. A telephone station comprising a port for connecting the station to a telephone network, a handset, encoding means coupled between the handset and the port for encoding and sending an identification signal comprising at least one d.t.m.f. tone pair, decoding means coupled to the port for decoding an identification signal received through the port, and connection means coupled between the handset and the port for coupling the port to the handset only if an identification signal decoded by the decoding means is acceptable.

19. Apparatus for controlling access to a telephone receiving station substantially as herein described with reference to the accompanying drawings.

20. A method of controlling access to a telephone receiving station substantially as herein described with reference to the accompanying drawings.