GB2208057A

GB2208057A - Telephone interface device

Info

Publication number: GB2208057A
Application number: GB08717760A
Authority: GB
Inventors: Robert Andrew Edge; David Pratt
Original assignee: INSTELEC Ltd; Barron McCann Ltd
Current assignee: INSTELEC Ltd; Barron McCann Ltd
Priority date: 1987-07-27
Filing date: 1987-07-27
Publication date: 1989-02-15
Also published as: GB8717760D0

Abstract

A modular coupler device 10 converts dialing pulses from a telephone 30 into multi-frequency coded signals which it supplies to apparatus, such as a computer, at the other end of a telephone line 20. Speech communication is not affected. The device may be used for credit clearance on banking transactions. An encryption device (41, Fig.4 not shown) may also be included. <IMAGE>

Description

Telephone Interface Device The present invention relates to a telephone interface device and more particularly to a device which permits the. use of a conventional telephone apparatus to transmit digital data along a telephone line without the need for an acoustic coupler etc.

Numerical data is at present transmitted along telephone lines by employing multi-frequency coded signals which are produced by dedicated devices connected to or comprising an acoustic or other coupling to the telephone line. Thus a single telephone connection cannot be used for both speech communication and digital data transfer.

The present invention seeks to provide a coupler device which overcomes this problem.

According to the present invention there is provided a coupler device for connection to a telephone line and to a telephone apparatus comprising means for producing dialling pulses, the coupler device comprising means for detecting dialling pulse signals, means for converting the dialling pulse signals into multifrequency coded signals and means for supplying the coded signals to the telephone line.

Preferred embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings of which: Fig 1 is a diagram of a coupler device in accordance with the present invention; Fig 2 is a schematic view of the connection of the device of Fig 1 to a telephone and a telephone line; Fig 3 is a view similar to Fig 2 of an alternative connection arrangement; and Fig 4 shows a modification of the device of Fig.l.

Fig 1 shows a coupler device 10 connected to a telephone (BT) line 20 and a telephone 30 incorporating a conventional dial for producing dialling pulses. The device 10 is line-powered and comprises a line interface 11 which handles line polarity reversal and employs current detect circuit (implemented as a current mirror) to detect disc dial pulses without affecting line characteristics.

Coupled to interface 11 is a threshold detector 12 which cleans up the pulses from the line interface and provides a level detection circuit and TTL compatible inter face. The output pulses from the threshold detector are fed to pulse count logic and status monitor means 13 which receives pulses from the threshold detection circuit and translates them into logic level outputs indicating off the hook status and decoded dialled digits. In addition it provides a valid data strobe output and a tone delay or inhibit signal.

The output of means 13 is fed via a decoder 14 to a tone generator logic circuit 15. This circuit consists of a row and column decoder, low and high counters, and low and high sine wave generators to realize a DTMF, (dual tone multi-frequency) or MF4 synthesizer. An output of circuit 15 is connected to the line interface 11. Respective clock signal generators (not shown) are provided for means 13 and circuit 15. The generators have different frequencies and may be independent or may be connected by respective dividers with different dividing ratios to a common source.

The coupler device is employed as follows. The telephone 30 is used to dial a number in the normal way. Once the connection has been established, speech communication can proceed in the usual way. However, if it is desired to transmit numerical data down the telephone line, the relevant digits are simply dialled on the telephone dial. If, say, a '7' is dialled, this causes seven pulses to pass down line 20. At the same time these pulses are detected by coupler 10 and converted into multi-frequency signals representing the number '7' which are fed by circuit 15 down line 20 after the seven dial pulses but before the next train of dial pulses corresponding to the next number to be dialled. The apparatus (eg a computer) at the far end of the telephone line 20 ignores the dial pulses, but detects and utilises the multi-frequency signals for data capture.If desired the coupler device can be provided with means for preventing the dialling pulses from reaching the computer.

One particularly advantageous application of the coupler 10 is in the transmission of an account number (eg of a credit card account); an automatic voice response (digitised or recorded) at the other end of the line clears a credit request. The voice response can be heard by the caller, since the coupler 10 does not interfere with normal operation of the telephone.

Multi-line voice response technology is in existence which will accept input from the unit and give rapid access to voice tracks. These voice response concentrators can readily connect to conventional computer interfaces.

The coupler can also be employed in other areas, such as personal banking, distributor purchase or enquiry services, remote mail box applications etc.

Thus the coupler services to turn a conventional telephone into a terminal which can transmit numeric data.

The installation of the coupler is easy and does not require attendance by telephone authority personnel.

It is extremely compact, being of approximately matchbox size. Thus it is easily portable and can be carried by a user to insert in any telephone line which he or she happens to be near. This cannot be done with existing DTMF telephones and terminals, which are extremely bulky. Furthermore, the device according to the present invention permits speech communication along the same telephone line.

The coupler is located in circuit between the line cord 31 of a telephone and the telephone socket 21, see Fig 2. The connection between the coupler and the telephone socket 20 may be via a cable 32, Fig 3.

Of course instead of a dial, telephone 30 may have a push-button key pad; this does not affect the operation of the coupler.

A switch (not shown) may be provided to switch the coupler "on" and "off", so that no line power is taken when it is not required.

The coupler device may be modified so as to be capable of encrypting transmitted data, for example as shown in Fig.4. An encryptor 41 comprising a non-volatile RAM is provided between decoder 14 and tone generator logic circuit 15. The encryptor 41 is controlled by a further decoder 42 which decodes incoming DTMF signals on the telephone line. This provides a security feature and, in a preferred mode, operates a follows.

The user dials a telephone number as before. An automatic voice at the other end instructs the user to enter his or her respective code number, e.g. PIN number. Entry of the PIN number tells a computer at the other end the identity of the user. The computer then performs a "handshake" with the encryptor 41 to check that a basic encryption code thereof is valid. Once this is validated the computer generates a random number which it then supplies to the encryptor for use throughout the subsequent communication. Depending on which number is received, the RAM within the encryptor 41 determines the way in which the data is to be encrypted. This is. similar to a scrambler operation.

The messages between the computer and the encryptor are all by means of DTMF signals.

The above modification has the advantage of providing a considerable degree of security since a correct user code number and a valid handshake are necessary to start data transfer, and encryption or scrambling occurs during data transfer. The compactness and relative cheapness of the coupler device permits it to be economically replaced if it is damaged or the code number becomes no longer secret.

After entering of the PIN or other user code number, there are several ways in which the next step may be initiated. Many existing button telephones already have so-called "hash" and "asterisk" keys; in this case either of these buttons may be used as an "enter" key to proceed to the next stage. Alternatively it can be arranged that no PIN number includes the number "zero", so that key "zero" can be used as the "enter" key. In another system, all PIN numbers have the same length, four digits say, so that dialling or pressing the fourth number is automatically treated as an enter instruction. In another modification, an "enter" instruction may be generated automatically after a predetermined interval of time. In all cases the "handshake" process provides back-up security.

Means may also be provided for effecting close down, i.e. terminating the data link. Where a telephone has both "hash" and "asterisk" keys, one way be used as an "enter" key and the other as a "close down" key.

Alternatively dedicated buttons may be provided for this purpose on the housing of the coupler device.

Any of the code number, handshake or scramble features may be omitted if desired and the coding methods and codes may be customized to the user's requirements.

The above-described coupler may be expanded to include a data display or an automatic data input device such as a bar-code reader or a slot or swipe reader. The coupler may be modified to receive data from a computer at the other end so the display may show data received by the coupler in addition to or instead of data transmitted by the coupler.

Claims

1. A coupler device for connection to a telephone line and to a telephone apparatus comprising means for prqducing dialling pulses, the coupler device comprising means for detection dialling pulse signals, means for converting the dialling pulse signals into multi-frequency coded signals and means for supplying the coded signals to the telephone line.

2. A coupler device according to claim 1 comprising a separate module with connection means permitting it to be inserted between a telephone socket and a plug and/or lead attached to a telephone apparatus.

3. A coupler device according to claim 1 or 2, comprising encryption means which are arranged to detect the dialling pulses and to convert them into encrypted multi-frequency signals.

4. A coupler device according to claim 3, wherein the encryption means comprise a random access memory (RAM).

5. A coupler device according to claim 4, wherein at least part of the RAM contains a basic encryption code which it supplies when suitably interrogated.

6. A coupler device according to claim 4 or 5, wherein at least part of the RAM contains a plurality of output-signal-modifying codes, one of which is selected upon receipt of a suitable instruction signal.

7. A coupler device according to any preceding claim, comprising an "enter" button to instruct dialled information to be supplied to the telephone line.

8. A coupler device according to any preceding claim, comprising a "close-down" button to terminate a communication.

9. A coupler device substantially as herein described with reference to Fig.l or Fig.4, and Fig.2 or Fig.3 of the accompanying drawings.

10. The combination of a telephone capable of producing dialling pulses and a coupler device in accordance with any preceding claim.

11. A method of transmitting digital data substantially as herein described with reference to Fig 1 or Fig 4, and Fig 2 or Fig 3 of the accompanying drawings.