WO1999022506A2 - Telephone system with answering machine - Google Patents
Telephone system with answering machine Download PDFInfo
- Publication number
- WO1999022506A2 WO1999022506A2 PCT/IB1998/001656 IB9801656W WO9922506A2 WO 1999022506 A2 WO1999022506 A2 WO 1999022506A2 IB 9801656 W IB9801656 W IB 9801656W WO 9922506 A2 WO9922506 A2 WO 9922506A2
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- telephone
- answering machine
- telephone system
- line
- tone
- Prior art date
Links
Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04M—TELEPHONIC COMMUNICATION
- H04M1/00—Substation equipment, e.g. for use by subscribers
- H04M1/64—Automatic arrangements for answering calls; Automatic arrangements for recording messages for absent subscribers; Arrangements for recording conversations
- H04M1/65—Recording arrangements for recording a message from the calling party
- H04M1/654—Telephone line monitoring circuits therefor, e.g. ring detectors
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04M—TELEPHONIC COMMUNICATION
- H04M1/00—Substation equipment, e.g. for use by subscribers
- H04M1/64—Automatic arrangements for answering calls; Automatic arrangements for recording messages for absent subscribers; Arrangements for recording conversations
Definitions
- the invention relates to a telephone system comprising at least one telephone subset and an answering machine connectible, in parallel, to an outside telephone line.
- the invention also relates to a method of parallel set detection in such a telephone system.
- the invention further relates to an answering machine for use in a telephone system in which the answering machine and at least one telephone subset are connectible in parallel.
- the telephone answering machine When a customer buys a stand-alone answering machine or an answering machine incorporated in a telephone subset, said machine is usually operated in parallel to the conventional telephone.
- the telephone answering machine When the telephone answering machine is on-line, it will monitor the line for incoming calls. This monitoring can also taken place when there are still other persons in the house to pick-up the telephone when a call comes in.
- the (telephone) answering machine picks up the telephone to respond to the incoming call, it will start playing the prerecorded message and will subsequently record the message which the calling party wants to leave behind. During this period of time, one of the persons in the house can pick-up the parallel-connected telephone. Then, one of the requirements is that the answering machine has to stop its operation and finish the call, leaving the parallel set, i.e. the telephone, in charge of the call. To this end, the answering machine should be able to detect that the parallel set has been picked up.
- the telephone system comprises a first line terminal and a second line terminal, the answering machine comprising tone-generating means for generating a probe tone from the answering machine to the first and second line terminals, and detection means for detecting a change in reflected residue of said probe tone in response to an impedance change between the outside telephone line and the telephone system.
- the present invention relies on the fact that the total impedance seen by the outside telephone line changes when a parallel set is picked up in the telephone system.
- the impedance of the telephone subset corresponds to the impedance of the telephone line, when the telephone subset is in the off-hook position while the answering machine is inactive.
- the impedance of the answering machine corresponds to the impedance of the outside telephone line.
- the impedance of the telephone system seen by the telephone line will change.
- a probe tone is generated in the answering machine and directed towards the outside telephone line. Due to the change in the telephone system impedance, a changed residue of said generated probe tone will be reflected, for example, at the line terminals.
- a probe tone of this kind allows a number of possible signals to be generated and provides a more accurate detection so that the reliability of the measurement is . increased.
- the tone when reflected at the line terminals, will not be heard by the user, both at the far and near end, of the telephone because it falls outside the frequency range that covers telephone calls.
- out-of-band is in fact outside the speech band.
- the probe tone has a frequency within a type approval frequency mask.
- the frequency of the tone generated within the answering machine and sent to the telephone line lies within the type approval frequency mask.
- the detection means comprise a bandpass filter and an energy detector.
- a bandpass filter with a center frequency around the frequency of the generated tone is used, so that the energy content of the reflected residue can be measured and compared with the energy content of the reflected residue before the impedance change.
- the detector is provided with a detection window around the energy level of the reflected residue before the impedance change.
- the detection means comprise a correlator.
- a correlator is preferred to measure the reflected residue and thus to ascertain a parallel set pick-up.
- the invention further relates to a method of parallel set detection in a telephone system as described above.
- the invention also relates to an answering machine for use in a telephone system in which the answering machine and at least one telephone subset are connectible in parallel.
- Figures 1(a) and 1(b) are simplified basic diagrams of a telephone system according to the invention, comprising a telephone subset and an answering machine connected, in parallel, to an outside telephone line;
- Figures 2(a) and 2(b) show a possibility for the received reflected frequency spectrum of a transmitted outgoing message plus probe tone due to an impedance change as the result of a parallel set pick-up, before and after parallel set pick-up;
- Figure 3 is a block diagram of a digital signal processor-based parallel set detection
- Figure 4 is a block diagram of an analog IC which can be used in the telephone system and answering machine according to the present invention to perform a parallel set detection.
- Figures 1(a) and 1(b) are simplified basic diagrams of a telephone system 1 comprising a telephone handset, or subset 3, and an answering machine 5.
- Figure 1(a) shows a system in which the telephone subset 3 is in the on-hook position while the answering machine is active
- Figure 1(b) shows a system in which the telephone subset 3 is in the off-hook position and the answering machine 5 is inactive.
- Reference numeral 7 denotes a telephone exchange to which the telephone system 1 with a first line terminal 11 and a second line terminal 13 is connected via an outside telephone line 9 in order to receive messages from, and send messages to, the telephone exchange 7.
- the telephone subset 3 has a first terminal 15 and a second terminal 17, and the answering machine 5 has a first terminal 19 and a second terminal 21.
- the answering machine 5 and the telephone subset 3 are connected, in parallel, to the first line terminal 11 and the second line terminal 13 of the telephone system 1.
- the telephone subset 3, the answering machine 5 and the telephone exchange 7 have an impedance de
- the answering machine When the answering machine is on-line, it will monitor incoming calls. When the incoming message is being recorded, the telephone subset may be picked up. A requirement is now that the answering machine stops operating and leaves the telephone subset in charge of the call. To detect whether the telephone is in the on-hook or off-hook position, i.e. whether a parallel pick-up occurs in the telephone system, the answering machine is provided with probe tone-generating means. The generated probe tone is sent towards the line terminals of the telephone system.
- the impedance of the telephone system will change.
- Figure 1(a) shows the situation in which the answering machine 5 is active (switch 28 closed) and the telephone subset 3 is in the on-hook position (switch 29 open).
- an impedance mismatch may or may not be present, depending inter alia on the quality of the telephone system and line length variations.
- a parallel set pick-up in the case of absence of a mismatch, a change in impedance between the telephone system and the telephone exchange will cause a mismatch.
- An already existing mismatch in impedance between the telephone system and the telephone exchange will increase or decrease due to the parallel set pick-up. Consequently, in all cases mentioned here, the reflection of the probe tone generated in the answering machine will be different before and after the parallel set pick-up which causes a change in impedance (mis)match.
- a difference in telephone exchange impedance due to line length variations does not affect the principle of detection of the changed reflected residue.
- the probe tone frequency is out-of-band, i.e. said frequency has a value which is different from the frequency band for outgoing messages. Consequently, the probe tone cannot interfere with the outgoing message, i.e. speech messages.
- the probe tone frequency preferably has a value in the range between 8 and 15 kHz.
- Figure 2(a) shows a possibility for the transmitted frequency spectrum and the received reflected frequency spectrum of an outgoing message and the probe signal before a parallel set pick-up.
- Figure 2(b) shows the transmitted frequency spectrum and the received reflected frequency spectrum of an outgoing speech message and the probe signal after a parallel set pick-up.
- the transmitted spectrum is indicated by a solid line and the received spectrum is indicated by a broken line.
- Both Figures illustrate a situation in which already a mismatch between the telephone line and the telephone system before a parallel set pick-up. When there is no outgoing message, the spectrum of the outgoing message will disappear.
- the envelope denoted by e in Figures 2(a) and 2(b) is the type approval frequency mask. It indicates the range of frequencies in combination with the signal level which a transmitted signal has to obey. Said ranges are imposed by the telephone exchange.
- the probe tone may be a continuous signal or a pulsed signal.
- FIG. 3 shows a block diagram of parallel set detection based on a digital signal processor.
- the answering machine 5 comprises a block 33 besides the normal answering machine functionality 35.
- Block 33 comprises tone-generating means 37.
- the probe tone is generated independently of the presence of an outgoing message and is sent towards the line terminals. When there is an outgoing message, the probe tone and the message are jointly sent towards the terminals 19, 21, and the line terminals 11, 13, respectively.
- the changed reflected residue is detected in detection means 39. A change in reflection occurs due to the pick-up of a parallel set. Reflection of the residue takes place, for example, at the line terminus 11, 13.
- Detection of the reflected residue can be performed by using a bandpass filter 41 at the frequency of the generated tone, and an energy detector 43.
- the energy detector is provided with a detection window on an energy level corresponding to the energy level of the reflected residue before parallel set pick-up. This is illustrated in Figures 2(a) and 2(b) .
- the detection window extends through an energy range ⁇ and is concentrated around the energy level of the reflected residue before parallel set pick-up. When the energy level of the reflected residue after parallel set pick-up is outside this range, a change in reflected residue is ascertained and the parallel set pick-up will thus be detected.
- the detection based on a correlation technique by using a correlator 45 is preferred.
- blocks 43 and 45 are thus exchangeable.
- the described parallel set detection employing a digital signal processor can be used in all answering machine applications in a customer environment, together with a PSTN (Public Service Telephone Network) line. Examples are stand-alone answering machines, analog cordless telephones with an answering machine in the base station, digital cordless telephones with an answering machine in the base station and add-on cards for PC- based answering machines.
- PSTN Public Service Telephone Network
- FIG. 4 is a possible diagram of an integrated circuit-based parallel set detection. Only the integrated circuit part 50 of the answering machine is shown. A probe tone X(t) is generated in an oscillator 51, coupled to the telephone subset line and sent towards the line terminals 15, 17, .and also the line terminals 11, 13 of the telephone system. The change in reflected residue is measured by means of a detector 53, the output 55 of which can be supplied to a microcontroller so as to deactivate the answering machine.
- the invention here presented allows detection of a parallel set pick-up by using remote sensing techniques.
- a probe tone is generated in the answering machine and is sent towards the outside telephone line.
- This effect can be detected, for example, at the line terminals of the telephone system.
- the reflection of the probe tone is measured without the use of external components or expensive components needed for other applica- tions within the system.
- a digital signal processor which is present in answering machines, that are currently available on the market.
- the digital signal processor allows software programmability of both the threshold levels and country specific parameters.
- the telephone system described hereinbefore is not restricted to a system comprising an answering machine and one telephone subset, but the present invention is also applicable in telephone systems comprising an answering machine and a plurality of telephone subsets.
Abstract
Description
Claims
Priority Applications (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP52358399A JP2001507554A (en) | 1997-10-28 | 1998-10-19 | Telephone system with answering machine |
EP98946667A EP0968598A2 (en) | 1997-10-28 | 1998-10-19 | Telephone system with answering machine |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP97203344 | 1997-10-28 | ||
EP97203344.3 | 1997-10-28 |
Publications (2)
Publication Number | Publication Date |
---|---|
WO1999022506A2 true WO1999022506A2 (en) | 1999-05-06 |
WO1999022506A3 WO1999022506A3 (en) | 1999-08-12 |
Family
ID=8228874
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/IB1998/001656 WO1999022506A2 (en) | 1997-10-28 | 1998-10-19 | Telephone system with answering machine |
Country Status (5)
Country | Link |
---|---|
EP (1) | EP0968598A2 (en) |
JP (1) | JP2001507554A (en) |
KR (1) | KR20000069724A (en) |
CN (1) | CN1249100A (en) |
WO (1) | WO1999022506A2 (en) |
Citations (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE3011758A1 (en) * | 1980-03-26 | 1981-10-01 | Siemens AG, 1000 Berlin und 8000 München | Telephone party line circuit - has voltage monitoring circuit providing signal to switch off answering machine for A=subscriber and switch on B=subscriber's appts. |
US5392332A (en) * | 1992-05-27 | 1995-02-21 | Phonemate, Inc. | Shared line telephone answering system with a telephone line-powered disconnect module |
US5481596A (en) * | 1994-05-26 | 1996-01-02 | At&T Corp. | Auxiliary baseband telephone interface for an answering machine |
US5579377A (en) * | 1994-11-18 | 1996-11-26 | Rogers; Laurence S. | Remote-control telephone answering system and method |
-
1998
- 1998-10-19 EP EP98946667A patent/EP0968598A2/en not_active Withdrawn
- 1998-10-19 KR KR1019997005807A patent/KR20000069724A/en not_active Application Discontinuation
- 1998-10-19 JP JP52358399A patent/JP2001507554A/en active Pending
- 1998-10-19 WO PCT/IB1998/001656 patent/WO1999022506A2/en not_active Application Discontinuation
- 1998-10-19 CN CN98802931A patent/CN1249100A/en active Pending
Patent Citations (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE3011758A1 (en) * | 1980-03-26 | 1981-10-01 | Siemens AG, 1000 Berlin und 8000 München | Telephone party line circuit - has voltage monitoring circuit providing signal to switch off answering machine for A=subscriber and switch on B=subscriber's appts. |
US5392332A (en) * | 1992-05-27 | 1995-02-21 | Phonemate, Inc. | Shared line telephone answering system with a telephone line-powered disconnect module |
US5481596A (en) * | 1994-05-26 | 1996-01-02 | At&T Corp. | Auxiliary baseband telephone interface for an answering machine |
US5579377A (en) * | 1994-11-18 | 1996-11-26 | Rogers; Laurence S. | Remote-control telephone answering system and method |
Also Published As
Publication number | Publication date |
---|---|
JP2001507554A (en) | 2001-06-05 |
CN1249100A (en) | 2000-03-29 |
EP0968598A2 (en) | 2000-01-05 |
WO1999022506A3 (en) | 1999-08-12 |
KR20000069724A (en) | 2000-11-25 |
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