GB2251765A

GB2251765A - Interactive telephone announcement apparatus

Info

Publication number: GB2251765A
Application number: GB9100762A
Authority: GB
Inventors: Jeffrey Wilson; Michael Anthony Diplock
Original assignee: Telsis Ltd
Current assignee: Telsis Ltd
Priority date: 1991-01-14
Filing date: 1991-01-14
Publication date: 1992-07-15
Anticipated expiration: 2011-01-14
Also published as: GB9100762D0; GB2251765B

Abstract

Interactive telephone announcement apparatus includes an audio signal generator 12 for transmitting speech- processed audio signals on a telephone line 11, and an interactive processor 18 for receiving response signals from a caller on the telephone line 11. In order to reduce interference on the interactive processor 18 resulting from the signals from the audio signal generator 12, and thereby improve the ability of the apparatus to distinguish the caller's response from the generated audio signals, a processing circuit such as an echo canceller 17 effectively balances and subtracts the generated audio signals from those on the telephone line 11 such that the signals received by the interactive processor 18 are made up substantially only of the caller's speech signals. This makes it possible for the caller to interrupt an announcement, rather than have to wait until the announcement has finished. <IMAGE>

Description

INTERACTIVE TELEPHONE ANNOUNCEMENT APPARATUS This invention relates to interactive telephone announcement apparatus, that is to apparatus which can interact in response to telephone requests from a caller replying to announcements from the apparatus.

Current interactive telephone announcement equipment can interact with a caller in a number of ways including dual-tone multi-frequency (DTMF) tone signalling, voice operated switching and speech recognition. The announcement equipment requests information from the caller who may then have a specific period in which to respond. The announcement equipment is normally quiet during this period so that the caller can be heard. To allow the caller to interact with the announcement equipment in a more "natural" way, it would be desirable for the caller to be able to interrupt it without, for instance, having to listen to the whole announcement, or in order to make a choice from a long list of options. However, it can be difficult for an interactive processor controlling the announcement equipment to distinguish a caller's voice from the signal generated by the announcement equipment itself.One way around this problem is for the caller to use DTMF signalling. This allows for an interrupt facility because tone signalling can be more readily detected even in the presence of speech and other audio signals. However, not all callers use DTMF tone phones so that there is a requirement for a voice interrupt (VINT) facility on interactive telephone announcement equipment which allows for the interruption of the announcement by the caller's voice. Moreover, rather than merely providing a VINT facility in which the equipment is interrupted by any sound made by the caller, it may be desired for the equipment to recognise specific words spoken by the caller, so that the interactive reaction of the equipment is dependent on the spoken word or words. In this case, DTMF signalling will not help, even if it is available.

According to the present invention there is provided interactive telephone announcement apparatus comprising: means for generating audio signals for transmission on a telephone line; interactive means for receiving signals from the telephone line and controlling a function of the apparatus in response to the received signals; and means for processing the signals from the audio signal generating means and the telephone line so as to reduce the generated audio signal component in the received signals supplied to the interactive means.

Preferably, the interactive processing means controls the audio signal generating means such that, for example, a long announcement may be interrupted and terminated.

The means for reducing the generated audio signal component may be in the form of an echo canceller whose use is known in reducing echoes in two-wire/four-wire telephone trunk networks.

The invention will now be further described, by way of illustrative and non-limiting example, with reference to the accompanying drawings, in which: Figure 1 is a block diagram of a known four-wire to two-wire hybrid circuit telecommunications arrangement; Figure 2 is a block diagram of a known echo-cancelling arrangement in a telephone circuit; Figure 3 is a block diagram of an interactive telephone announcement apparatus according to an embodiment of the invention; and Figure 4 is a development of part of the apparatus shown in Figure 3.

In order that the invention may be more readily understood, a known hybrid circuit arrangement for interconnection in a four-wire to two-wire telephone circuit including an echo canceller will initially be described with reference to Figures 1 and 2.

Figure 1 shows a block diagram of a standard use of four-wire to two-wire hybrid circuits in telecommunications, in which telephones 1 and 1' are connected to two-wire telephone lines 2 and 2', and hybrid circuits 3 and 3' are respectively connected between the two-wire telephone lines 2 and 2' and a four-wire trunk line circuit including separate lines 4 and 4'. The hybrid circuits 3 and 3' are used to convert the standard subscribers' two-wire circuit to the four-wire trunk line circuits used to connect exchanges. For instance, speech signals from the telephone 1' are transmitted along the line 2', enter the hybrid circuit 3', are amplified if necessary and diverted to the line 4' of the four-wire trunk network. The speech signal then enters the hybrid circuit 3, where it is amplified if necessary and diverted to the earphone of the telephone 1 via the line 2.Similarly, speech signals from the telephone 1 are transmitted along the line 2 into the hybrid circuit 3, where they are amplified if necessary and diverted to the line 4 of the four-wire trunk network. This speech signal then enters the hybrid circuit 3', where it is amplified if necessary and diverted to the earphone of the telephone 1' via the line 2'. The use of the two-wire to four-wire speech network and the hybrid circuits 3 and 3' helps ensure that signal distortions are kept to a minimum in long-distance trunk calling as any repeater amplifiers (not shown) along the lines 4 and 4' should only deal with either an outgoing signal or an incoming signal.

Most hybrid circuits are not ideal due to line impedance mismatches and the like, and some incoming signal along the line 4' for instance, can be mixed with the outgoing signal along the line 4.

Microphone signals from the telephone 1' might therefore be received from the line 4 in the earphone of the telephone 1' after being mixed with outgoing signals in the hybrid circuit 3 from the telephone 1, thereby producing an echo effect resulting from the time taken for the signals to return to the telephone 1'. These speech echoes are undesirable.

Figure 2 shows the way in which a processor circuit, called an echo canceller 5, can be used to help diminish echoes from the microphone of the telephone 1, that travel along the line 4' from the hybrid circuit 3'. The echo canceller 5 is connected between the line 4 and a summing circuit 6 interposed between the hybrid circuit 3' and the line 4'. The echo canceller 5 also has an input directly from the line 4'. A speech signal travelling along the line 4 from the telephone 1 passes directly into the hybrid circuit 3 and is diverted and received by the telephone 1'; the speech signal is also passed to the echo canceller 5. From the echo canceller 5, the modified speech signal is supplied to the summing circuit 6 where it may combine with a speech signal from the telephone 1' and any echo of the speech signal from the telephone 1 caused by the hybrid circuit 3'.The function of the echo canceller 5 in this circuit is to modify, and if necessary delay shift the speech signal from the telephone 1 so that it will substantially cancel out the echo signal from the hybrid circuit 3' on combination with the speech signal from the telephone 1' and the echo signal from the hybrid circuit 3' travelling along the line 4'.

For this purpose, the echo canceller 5 is typically in the form of an adaptive filter. The echoes caused by the hybrid circuit 3' are initially estimated by the echo canceller 5 on the basis of the signals on the line 4, and the output from the subtraction of the estimated signal from the actual signal, namely the signal on the line 4', is used to modify the operation of the echo canceller 5 so as to minimise the error signal on the line 4', thereby minimising the echo from the far-end talker to the far-end listener at the telephone 1. Thus the echo canceller 5 must be able to estimate the impulse response between the two line connection sides of the hybrid circuit 3', and to handle any delay resulting from the distance of the echo canceller 5 from the hybrid circuit 3'.Characteristics of a suitable echo canceller are covered by the CCITT G165 standard.

The present invention makes use of a similar estimated signal subtraction technique, but applied in a different way to that of the echo cancelling method shown in Figure 2. As outlined above, a problem with existing interactive telephone announcement equipment is that it is not easy for a caller to interrupt an announcement from the equipment, since the caller's signal to the interactive processor will be swamped by the announcement signal. The announcement equipment is typically made up of an audio signal generator connected to the telephone line via an amplifier and a line interface hybrid circuit which provides the isolation. The interactive processor is connected via the hybrid circuit to "listen" to the line continuously for signals from the caller. Since the telephone line is a two-wire circuit, the interactive processor receives signals from both the announcement equipment and the caller, the caller's signal being at a much lower level because of the attenuation on the telephone line. Thus any interruption by the caller is unlikely to be distinguished by the interactive processor from the announcement equipment signals, and it is therefore in general necessary for the caller to await the end of the announcement before replying. This is the case for both voice interrupt and word recognition equipment.

Figure 3 shows a block diagram of an interactive telephone announcement apparatus according to one embodiment of the invention wherein a hybrid circuit 13 is connected to a telephone line 11. An audio signal generator 12 and an interactive processor 18 are also connected to the hybrid circuit 13. A signal from the audio signal generator 12 to the hybrid circuit 13 is amplified by an amplifier 15.

A signal from the hybrid circuit 13 to the interactive processor 18 is amplified by an amplifier 16. Between the audio signal generator 12 output and the interactive processor 18 is connected an echo canceller 17, in order to facilitate the interruption of the automatic telephone announcement apparatus by a telephone speech signal.

When the apparatus receives a call from a telephone caller, the audio signal generator 12 transmits a signal, such as a spoken request or statement, to the hybrid circuit 13 via the amplifier 15. The telephone caller can receive this audio signal by way of the line 11 connected to the hybrid circuit 13. The interactive processor 18 "listens" to the line 11 via the hybrid circuit 13 for a speech signal.

The amplifier 16 amplifies any signal from the hybrid circuit 13 to the interactive processor 18. To reduce interference from the audio signal introduced via the hybrid circuit 13, the echo canceller 17 is connected between the amplifier 16 and the interactive processor 18, with a further connection from the audio signal generator 12. The echo canceller 17 functions in a similar manner to that described with reference to Figure 2, in that the inputs from the audio signal generator 12 and from the amplifier 16 are balanced and subtracted so as to minimise the signal component from the audio signal generator 12 in the output of the echo canceller 17 supplied to the interactive processor 18.The signal received by the interactive processor 18 should therefore be substantially made up of only the speech signal from the caller, thus facilitating interaction between the caller and the interactive processor 18.

Preferably the interactive processor 18 can respond to DTMF as well as voice signals. Also, as discussed above, the interactive processor 18 may function either on a voice interrupt basis such that any sound from the telephone caller will be detected, or on a word recognition basis whereby only detection of a specific word or words will control a function of the apparatus. Typically, the audio signal generator 12 will run through a list of options, and the caller will respond when a particular option is reached. The interactive processor 18 detects the caller's response and modifies operation of the audio signal generator 12, such as by moving on the speech program to a different list of options.

Thus, the preferred apparatus allows a telephone user to call up, listen to and, if desired, interrupt a message stored in telephone announcement equipment. The caller listens to an announcement from the apparatus given by an audio signal generator. The apparatus includes an echo canceller to allow an interactive processor in the apparatus to receive a relatively pure and uncontaminated speech or other audio signal from the caller. The interactive processor can then act in response to the caller's speech or other signal by, for instance, causing the audio signal generator to shut down, stop a section of the announcement, modify the announcement or actuate some other system.

Figure 4 shows a development of the interactive telephone announcement apparatus made possible by applying the echo cancelling technique. Figure 4 shows only the interactive processor 18 and part of the audio signal generator 12. The audio signal generator 12 includes an option selector 20 and a number of option read-out blocks 22 which are intended to be representative of means for reading out individual spoken options from a list of options.

Previously-proposed announcement apparatus is set to read through the list of options in a predetermined order. If a caller responds slightly too late when a desired option is given, it is necessary for the caller to repeat the whole selection process, possibly even by initiating a new call, whereupon the list of options will be repeated fully. Use of the echo cancelling technique, which provides a more flexible form of interrupt or word recognition operation, allows an improved form of option selection. Assuming that the option selector 20 has already selected options n and n+1 in turn, and that the message associated with option n+2 is being read, if the caller realises that option n+1 was the one desired, he may respond whereupon the apparatus will request confirmation that option n+2 is correct.In the previously-proposed apparatus, failure by the caller to give the requested confirmation would lead to a different option list being selected for read-out or, at best, a return to the beginning of the current option list. In view of the improved ability of the apparatus to detect interruptions when an announcement is being provided by the audio signal generator 12, the arrangement shown in Figure 4 will respond differently to the caller's failure to confirm the message.

Thus if no confirmation has been received from the caller for option n+2, the option selector 20 will check a different option such as option n+1 and request confirmation of that option. Again if no confirmation is received, a further option such as option n+3 may be attempted. It will be apparent that the option selector 20 may be arranged to try options in any desired manner; in order to cover late or early responses from the caller, the succeeding options will typically be those before and/or after the option to which the caller actually responded.

Claims

1. Interactive telephone announcement apparatus comprising: means for generating audio signals for transmission on a telephone line; interactive means for receiving signals from the telephone line and controlling a function of the apparatus in response to the received signals; and means for processing the signals from the audio signal generating means and the telephone line so as to reduce the generated audio signal component in the received signals supplied to the interactive means.

2. Interactive telephone announcement apparatus according to claim 1, wherein the signal processing means comprises an adaptive filter operable to estimate initially the generated audio signal component in the received signals and thereafter to minimise the generated audio signal component on the basis of the output of the signal processing means.

3. Interactive telephone announcement apparatus according to claim 1 or claim 2, wherein the audio signal generating means is responsive to signals from the telephone line detected by the interactive means thereby to modify operation of the audio signal generating means.

4. Interactive telephone announcement apparatus according to claim 3, wherein the interactive means is responsive to voice interruption signals.

5. Interactive telephone announcement apparatus according to claim 3, wherein the interactive means is responsive to recognition of one or more specific words conveyed by the received signals.

6. Interactive telephone announcement apparatus according to claim 3, claim 4 or claim 5, wherein the audio signal generating means includes an option selector operable to select a predetermined sequence of option messages to be transmitted by the telephone line.

7. Interactive telephone announcement apparatus according to claim 6, wherein, upon signal detection by the interactive means during readout from the sequence of option messages, the audio signal generating means is operable to request confirmation that the currently read-out option message is that required and, in the absence of such confirmation, to modify the predetermined sequence of option messages.

8. Interactive telephone announcement apparatus according to claim 7, wherein, in the absence of the requested confirmation, the option selector is operable to select an option message adjacent in order to that last transmitted.

9. Interactive telephone announcement apparatus according to claim 8, wherein the selected adjacent option message is that immediately preceding the last transmitted option message.

10. Interactive telephone announcement apparatus substantially as herein described with reference to Figure 3, or Figures 3 and 4, of the accompanying drawings.