TELEPHONE EXCHANGE

Abstract: A telephone exchange transmits audible signals to a subscriber line to indicate exchange or network conditions. The audible signals to be transmitted to the subscriber line are selected (means 15) from one or more available audible signal sources (14, 16, 17, 18) according to the contents of a store location (20) for that subscriber line. Further store locations (25) are provided for each subscriber line to enable selection (means 21) of further audible signal sources (22, 23, 24) dependent upon the condition. The subscriber may alter the contents of his or her store location (20, 25) by dialling a special code. By dialling a special code the subscriber may initiate a call attempt using a predetermined series of dialled digits corresponding to the selected signal source (16, 17, 18), in response to the information heard.

Description: TELEPHONE EXCHANGE The present invention relates to telephone exchanges and more particularly to audible signals to be transmitted by the exchange to a subscriber line to indicate exchange or network conditions, e.g. that dialling is possible, or to indicate the progress of an attempt to establish a desired connection. Various systems have been proposed in which the conventional audible signals ('dialling-tone', 'engaged (busy) tone') etc are replaced by information- bearing signals such as advertising. According to one aspect of the present invention there is provided a telephone exchange comprising: (a) control means responsive to one or more call-progress conditions of a first subscriber line to route to the first subscriber line an audio source selected from a plurality of such sources; at least one of said audio sources having a respective second subscriber line associated with it; (b) means operable in response to assigned dialled signals from the first subscriber line to initiate a call attempt from the first subscriber line to the second subscriber line associated with the audio source. According to another aspect , there is provided a method of controlling a telephone exchange comprising the steps of responding to a call-progress condition of a first subscriber line by routing to the first subscriber line an audio message, selected from a plurality of such messages, and responding to an assigned dialled signal from the first subscriber line to initiate a call attempt from the first subscriber line to a second subscriber line associated with the selected audio message. The call-progress condition may for example, be the "off-hook, "line busy", or "dialled number invalid" condition The telephone exchange may include store having, for each of a plurality of subscriber lines connected to the exchange, a store location for containing a code word identifying one of a plurality of audio sources, the control means being operable to interrogate the store location corresponding to the calling subscriber line and to route to the calling subscriber line the audio source identified by the code word therein, and may further be provided with means operable in response to time-of-day data to change the code word in the corresponding store location so as to change the audio source to be selected for subsequent call attempts by that subscriber and/or means operable in response to stored customer-profile data to change the code word in the corresponding store location so as to change the audio source to be selected for subsequent call attempts by that subscriber. The code word may be changeable in response to assigned dialled signals from the subscribers telephone line. Some embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, in which, Figure 1 shows a digital local exchange, Figure 2 shows the construction of a digital concentrator, Figures 3 to 7 are flow charts showing the operation of the control unit 1 3 of Figure 2 for each of the following embodiments: Figure 3 - substitution of 'dial' tone with a subscriber-selectable audio source; Figure 4 - basic substitution of 'ringing' 'busy' and 'invalid number' tones with subscriber-selectable audio sources; Figure 5 - playing a subscriber-selectable audio announcement while withholding dialled digits; Figure 6 - playing a subscriber-selectable audio announcement while withholding dialled digits, with the further facility to select additional audio information linked to the initial audio announcement; Figure 7 - playing a subscriber-selectable audio announcement while withholding ringing current to a cailed subscriber's line. Referring to Figure 1 , a digital switch 1 is shown with connections 2 to other such exchanges and/or trunk exchanges of a telephone network, and connections 3 via digital concentrators 4 (and, if desired, remote concentrators 5) to analogue subscriber lines 6. Figure 2 shows the subscriber lines 6 connected to a number of subscriber line modules 7 within a digital concentrator 4, each line module 7 including ringing current injection, 2 wire to 4 wire conversion and analogue-to-digital and digital-to- analogue converters. Each line module 7 has a digital input and output connected to one of a number of digital switches 8, 9. Outgoing signals from a switch 8 pass via a tone injection unit 1 0 and thence to the digital switch 1 At this point also are connected receivers 1 1 for tone (DTMF) signalling. Similarly incoming signals pass from the switch 1 via a tone injection circuit 1 2. All these units 7-1 2 are connected to a concentrator control unit 1 3 in the form of a stored-program controlled processor. When a subscriber goes "off-hook", this is recognised by the line module 7 which triggers processes in the control unit 1 3 to route connections via the switches 8, 9 and to allocate one of the DTMF detectors 1 1 to recognise "dialling" by the subscriber. The fact that the subscriber is able to dial out is indicated to the subscriber by the control unit 1 3 enabling the passage of dial tone from a tone generator 14 via a switch 1 5 and tone injection unit 1 2. The exchange, as thus far described, is conventional, as is the exchange's response to detection of normal dialling. The exchange differs from conventional exchanges in the provision of substitute audio sources ( 1 6, 1 7, 1 8) providing signals, for example advertisements. Other sources, for example unit 1 9 providing interrupted dial tone may be provided to indicate a particular state of the subscriber line - for example that call- forwarding is in effect. It will be appreciated that all of these sources serve to provide a sound which the subscriber hears upon picking up his or her handset, i.e. the exchange's response to an off-hook condition. In order that the source to be heard can be selected, the concentrator module 4 includes a store 20 containing a storage location for each subscriber line, so that a code number stored therein can be interrogated by the control unit 1 3 to identify the source to be connected. It is envisaged that the material to be played may be selected to be appropriate to the customer, for example based on customer-profile data, possibly including geographical data. A facility may also be provided for the subscriber to change his/her chosen preference at any time by keying a special code (e.g. * 1 , * 2 etc.) which is received by the DTMF detector 1 1 and recognised by the control unit 1 3 which then writes the corresponding code number into the relevant location of the store 20. Next time the subscriber goes off hook, the new code number is present in the store 20 and the new preference ( 1 4, 1 6, 1 7, 1 8) is provided. The customer options may carry different tariffs - for example advertisers may pay for discounted call tariffs. It is important to note that the changing of code numbers in the store 20 serves only to select the desired dialling tone or substitute, and does not otherwise affect the service provided by the exchange to the subscriber With additional reference to Figure 3, the operation of the control unit 1 3 will now be described in more detail for the case of a subscriber going off hook, in which it is assumed that the code numbers entered in the store 20 are the numbers 1 4 and 1 6 to 1 8 used in Figure 2. Following detection of the subscriber's off hook condition by line module 7 and allocation of a concentrator switch and DTMF equipment, a check is made to determine whether call forwarding is activated for that subscriber's line If so, interrupted dial tone unit 1 9 is selected and the audio source routed to the subscriber via the switch 1 5 and the tone inject unit 1 2. If call forwarding is not activated, the control unit 1 3 reads the contents of the subscriber's storage location in the store 20 and selects the audio source unit identified therein. This may be the normal dial tone unit 14 or one of the substitute audio sources, units 1 6 to 1 8. The selected audio source is routed to the subscriber via the switch 1 5 and the tone inject unit 1 2. The allocated DTMF equipment monitors the subscriber's line for any keyed number or code while the audio source plays. If a substitute audio source from units 1 6 to 1 8 finishes playing before detection of a DTMF signal on the subscriber's line, the dial tone unit 14 will be selected and dial tone played. While dial tone is selected, a time-out operates in the normal way until either a DTMF signal is detected on the subscriber's line or the time-out expires, in the latter case the call attempt will be terminated by the control unit 1 3. Detection of DTMF indicates either that the subscriber has begun dialling the number of an intended called subscriber, or that a special code is being dialled to change the contents of a storage location or to respond to the information transmitted by the audio source. In particular, by dialling a special code prompted by the information in the audio source (e g "dial *9 to order"), a call may be initiated to a selected number Detection of DTMF will immediately suspend the playing of the currently selected audio source. If the subscriber dials the special code " *0", the control unit 1 3 will play a help announcement, listing the available audio sources and the corresponding codes to be entered. Entry of a valid code * 1 , * 2, * 3 or *4 will update the subscriber's storage location in the store 20 to indicate the new preference and an announcement will be played to confirm the identity of the selected audio source. Dial tone from unit 1 4 will then be played until the subscriber either enters another special code or dials a telephone number or until the time-out expires. Entry of a code, shown illustratively as ' * 9' in Figure 4, causes the control unit to read the current contents of store 20. If the code stored therein corresponds to one of the audio sources 1 6, 1 7, 1 8 a corresponding directory number is selected and transmitted as a set of dialled digits to set up a call from the subscriber to the advertiser or other information provider. When a call attempt is made, either in response to the prompt or otherwise, an alternative subscriber-selectable audio source may be played after dialling the number of the intended called subscriber rather than before, i.e. an alternative to ringing tone. In a conventional arrangement, dialled digits for setting up a telephone call are routed via the switch 1 and the network to the called subscriber's exchange (or, for a call to a subscriber on the same exchange, to the switch 1 ) . When the called exchange has succeeded in establishing a connection and applied ringing current to the called subscribers line, it signals this fact back to the originating exchange where the control unit 1 3 causes injection of ringing tone via the injection unit 1 2. If the call fails, either because the dialled number is invalid or because the called party is engaged, an alternative message may be played, as will be discussed later. In the simplest version of ringing tone substitution, an audio signal to indicate ringing is selected by the control unit 1 3 via a switch 21 from alternative sources 22 (conventional ringing tone) 23 or 24 (messages) . The current selection is indicated by a code stored in a store 25 with a location for each subscriber analogous to the store 20 (in fact a single store might be used; or the functions of the stores 20 and 25 might be performed by allocated areas of a general purpose store in the control unit 1 3 itself) . Operation of the control unit 1 3 in these circumstances is shown in the flow chart of Figure 4 Note from Figure 4 that the opportunity is provided for the subscriber, by dialling one of a further set of special codes, to alter the contents of his or her store location in the store 25 to indicate a preference for one of the audio sources 22 to 24, to be played following dialling of the telephone number of the intended called subscriber. The help announcement discussed with reference to Figure 3 may be further arranged to include, in the listing of the available audio sources, the option of selecting audio source units 22 to 24 for use after dialling of the called subscriber's number. A disadvantage of the simple version of ringing tone substitution described above is that the calling subscriber hears the chosen sound for only so long as it takes for the called subscriber to answer If preferred, therefore, completion of the call may be deliberately delayed to allow the caller to hear a desired message. This could be achieved either by buffering the dialled digits at the originating exchange (e.g. in a buffer 26), or by allowing continuation of the call set up process up to the point where the called exchange has verified that the called subscriber line is available to accept the call, whereupon the remote exchange awaits clearance before sending ringing current to the called line. In order to avoid delaying urgent or emergency calls, it is highly desirable not only that the calling subscriber should be able to override this delay, but that the called subscriber should not be inhibited from making or receiving other calls while a first calling subscriber is listening to a substitute announcement before proceeding to call completion. Thus, according to a yet another embodiment of the invention, for which the operation of the control unit 1 3 is shown in Figure 5, call processing is suspended within the calling subscriber's originating exchange after dialling the telephone number of an intended called subscriber, the dialled digits being buffered in a buffer 26 while an audio source is played. The audio source is selected, according to the contents of a store location for that calling subscriber's line within the store 25, from the available audio source units 22 or 23 shown in Figure 2 for this example. According to Figure 5, after buffering the dialled digits, the control unit 1 3 reads the subscriber's store location in the store 25. If the conventional audio source unit 22 is indicated, then the buffered digits will be released immediately to the network for the call to proceed normally, conventional ringing tone being routed to the calling subscriber if the called subscriber's line is available to receive the call attempt. If substitute audio source unit 23 is indicated, the control unit 1 3 will route the audio announcement to the subscriber line via the switch 21 and tone inject unit 1 2. Meanwhile, the allocated DTMF detector will monitor the subscriber's line for any keyed number or code while the audio source plays. If audio source unit 23 finishes playing before detection of a DTMF signal on the subscriber's line, the buffered digits will be released to the network and the call attempt will proceed normally. However, if the subscriber dials a special code, e.g. " #" , then the selected announcement will be immediately suspended and the dialled digits released to the network. A variation on this embodiment is described with reference to Figure 6, in which the control unit 1 3 is arranged to allow a calling subscriber to listen to a two part announcement, the second part being selected following the entry of a special code. In this example, the audio source unit 24 (advertising) of Figure 2 provides a two part announcement. Whilst the first part of the announcement plays, the allocated DTMF detector monitors the subscriber's line for any keyed number or code. Dialling a "#" will immediately abort the announcement and release the dialled digits to the network for the call to proceed normally. Otherwise, the first part of the announcement prompts the subscriber to enter a code, " *7" for instance, if he or she wishes to hear further advertising. For example, "Bloggs Foodstores offer you 5 pence off the cost of this call. Press *7 to accept and hear details of this week's grocery offers". If the user keys " * 7" then source 24 plays advertising. When the advertising has finished the buffered digits are released to the network and the call proceeds normally. If the user does nothing after the first part of the announcement, the buffered digits are released after a predetermined time-out period. Once again, if required, an announcement can be aborted at any stage by the subscriber entering a "#" , although in this example, abortion of the second part of the announcement before completion may be recorded by the control unit 1 3 and the entitlement to the offered call discount withdrawn. In yet another embodiment of the invention in which the dialled digits are not buffered, but rather are passed to the (remote) exchange for routing of the call, these digits will be accompanied by an instruction to that exchange to refrain (whilst otherwise processing the call normally) from applying ringing current to the called subscriber line. Once the called exchange has signalled to the calling exchange that the call is ready to proceed, the latter plays to the calling subscriber the audio source selected by the contents of the calling subscriber's store location in the store 25 and, on completion of the announcement or abortion by the calling subscriber, signals to the called exchange to release ringing, and applies normal ringing tone (or some other selected sound) to the calling line. Referring to Figure 7 it can be seen that, after forwarding the dialled digits to the called exchange and following receipt of a call completion signal indicating that the called subscriber's line is ready to receive a call, the control unit 1 3 reads the calling subscriber's store location in the store 25 and selects the audio source unit indicated therein. If the conventional ringing tone unit 22 is selected, the call will immediately proceed normally. Selection of one of the substitute audio source units 23 or 24 will result in the announcement being played to the calling subscriber in the same way as for the other embodiments. Once again, the calling subscriber may abort the announcement and proceed immediately with the call by entering the code "#" at any time while the announcement plays. In order to avoid inhibiting the called subscriber from either making calls or receiving calls from other subscribers while the first calling subscriber listens to the selected announcement, the control unit 1 3 checks for a 'busy' signal being returned from the called exchange indicating that either the called subscriber's line has gone off-hook to make a call or that another incoming call is being received thereon. If such a 'busy' signal is received, a flag is set by the control unit 1 3 to record that the called subscriber's line is 'busy' . When the announcement finishes, or if the calling subscriber aborts it after the setting of the 'busy' flag, busy tone will be routed to the called subscriber's line as normal. If the called subscriber's line remains ready to accept the call ('busy' flag not set), then upon completion of the announcement or abortion by the calling subscriber, the calling exchange signals to the called exchange to release ringing current and to proceed with the call attempt as normal. The concept of substituting alternative audio sources for conventional tones may be extended to other tones, for example the "busy" ("engaged") tone, or the "number unavailable" tone. The control unit 1 3 would be arranged to allow selection of the substitute audio source by the same method as for the embodiments described above, using a store location for each subscriber line. As shown in Figures 3 and 4, when a dialled number is sent to the 5 network, if a 'line busy' or 'number invalid' signal is returned an appropriate message is played (Figure 4) and the control unit 1 3 then reads store 20 (Figure 3) to select the appropriate announcement. The control unit 1 3 may alternatively be arranged to select an audio source from store 25, or a further store with a different message specific to 'busy' or 'invalid number' tone replacement, instead of store 1 0 20 as illustrated.

Claims: CLAIMS 1 . A telephone exchange comprising: (a) control means responsive to one or more call-progress conditions of a first subscriber line to route to the first subscriber line an audio source selected from a plurality of such sources; at least one of said audio sources having a respective second subscriber line associated with it; (b) means operable in response to assigned dialled signals from the first subscriber line to initiate a call attempt from the first subscriber line to the second subscriber line associated with the selected audio source. 2. A telephone exchange according to claim 1 in which the call-progress conditions include one or more of the "off-hook", "line busy" or "dialled number invalid" conditions. 3. A telephone exchange according to claim 1 or claim 2, including store means having, for each of a plurality of subscriber lines connected to the exchange, a store location for containing a code word identifying one of a plurality of audio sources, the control means being operable to interrogate the store location corresponding to the calling subscriber line and to route to the calling subscriber line the audio source identified by the code word therein. 4. A telephone exchange according to claim 3 including means operable in response to time-of-day data to change the code word in the corresponding store location so as to change the audio source to be selected for subsequent call attempts by that subscriber. 5. A telephone exchange according to claim 3 or 4 including means operable in response to stored customer-profile data to change the code word in the corresponding store location so as to change the audio source to be selected for subsequent call attempts by that subscriber. 6. A telephone exchange according to claim 5 including means operable in response to assigned dialled signals from a subscriber line to change the code word in the corresponding store location so as to change the audio source to be selected for subsequent call attempts by that subscriber. 7. A method of controlling a telephone exchange comprising the steps of responding to a call-progress condition of a first subscriber line by routing to the first subscriber line an audio message, selected from a plurality of such messages, and responding to an assigned dialled signal from the first subscriber line to initiate a call attempt from the first subscriber line to a second subscriber line associated with the selected audio message. 8. A method according to claim 7 in which the call-progress conditions include one or more of the "off-hook", "line busy" or "dialled number invalid" conditions. 9. A method according to claim 7 or 8 in which the audio message is selected according to the identity of the first subscriber line. 10. A method according to claim 7, 8 or 9 in which the audio message is selected according to time-of-day data. 1 1 . A method according to claim 9, including the steps of obtaining, in response to the call progress condition of the first subscriber line, a code word from a store location, said store location being selected from a plurality of store locations according to the identity of the first subscriber line, said code word identifying one of the plurality of audio messages. 1 2. A telephone exchange, substantially as hereinbefore described with reference to the accompanying drawings.

Inventors: MARTUCCI GIUSEPPE, MARTUCCI, GIUSEPPE
Applicants: BRITISH TELECOMM, MARTUCCI GIUSEPPE, BRITISH TELECOMMUNICATIONS PUBLIC LIMITED COMPANY, MARTUCCI, GIUSEPPE
Application year: 1998
Main classification: H04M3
IPC codes: H04M3