Patent GB-1054038-A (GB)
IPC: H04M1/65
Abstract: 1,054,038. Telephone answering machines. ROBOPHONE Ltd. Sept. 19, 1963, No. 36962/63. Heading H4K. [Also in Division G5] A telephone answering machine having facilities for recording messages in the subscriber's absence is provided with means whereby the subscriber may ring up his sub-station and; by transmitting the appropriate code signal, cause the reproduction over the line of messages recorded during his absence. The described embodiment utilized two tones of different predetermined frequency the first of which is maintained for a predetermined time before the second commences. The machine may be provided with means whereby it can be interrogated more than once by arranging that, once the machine has been successfully interrogated, it steps back in the recording to a position before that in which the interrogating code signal is recorded so that the following recorded message erases the interrogating signal. Tape mechanism details. Fig. 1 shows the tape deck which records the incoming messages and replays them to the subscriber when required and comprises a tape reel 2 from which, during record or playback, the tape passes over erase head 8, record-playback head 9, and capstan 14 to tape reel 83. Tape transport is controlled by solenoid 17 which brings pinch roller 15 into engagement with the tape on capstan 14. Tape reel brakes are controlled by solenoid 7, the take-up spool is driven via belt 13 and a friction clutch from capstan 14, and tape rewind is provided by solenoid 20 moving the reel carrier 2 into engagement with the spindle 4 of the capstan motor 4, the capstan being driven from the motor 4 by gearing (not shown). Guides 10 and 11 form contact members which are bridged by a metal foil on the tape to form a limit switch. The answering machine announcements are carried on a tape loop 21 on the announcement deck shown in Fig. 2. The tape loop is driven, by a capstan 24 rotated via a belt by motor 27, past a replay head 30. A micro switch 29 is provided to be operated by a thickening 28 on the tape to stop the tape after the announcement has been completed. Machine operation.-Signals from the telephone line are applied to terminals 31, 32 of Fig. 3. Ringing pulses are applied via transformer 36 and rectifier 35 and cause the operation of relay A via transistor Q50. Contacts A1 of relay A complete a charging circuit for capacitor 37 which charges to a potential at which transistor Q1 conducts and energizes relay B. Contact B1 changes over to connect the base of transistor Q1 to a capacitor 42 which is maintained charged, via transistor amplifiers Q2, Q3, and Q4, by the output of the amplifier rectifier unit 54 whose input is connected to line transformer 36, thus while signals remain on the line relay B is maintained operated. Contacts B2 close to complete a D.C. path between terminals 31 and 32 thus signalling acceptance of the call, and contacts B3 change over to disconnect the transformer 36 from the ringing detector and connect it to the record playback circuits. Contact B6, which originally connected capacitor 44 to a charging source, on operation of relay B energizes relay C which, via micro switch contacts 29 and contacts C1, self holds and causes, over contacts C2, the energizing of announcement loop drive motor 27, and the connection of the announcement replay head 30 to the telephone line via amplifier 49, contacts C3, B3, and transformer 36. After the announcement has been played the micro switch 29 is opened by the thickening on the tape and relay C drops out so connecting the telephone line to the record amplifier 51 over contact C3, and energizing the capstan motor 4 over contact C2 instead of the announcement motor 27. The machine will then record any incoming message. Signals on the line are monitored in amplifier rectifier 54 and a gap in the speech exceeding a predetermined minimum allows the charge on capacitor 42 to leak away so that transistor Q1 cuts off and relay B releases to restore the circuit ready to receive a subsequent call. Similarly a continuous tone on the line, e.g. dialling tone, is applied via unit 54 and transistor Q2 to cut off transistor Q5, which, if the tone is maintained for a time of 15 seconds, i.e. the charging time constant of capacitor 56 through resistor 58, turns on transistor Q6, and so cuts off transistor Q7 again causing relay B to release and disconnect the machine from the line. If during the time allocated for recording an incoming message the caller produces the appropriate interrogation signal, the signal appears at point 99 on the output of amplifier 51 and is detected in the interrogation signal detector, described below, and operates for a short time relay D. Over contacts D1 this causes the relay E to be energized and to self hold over contacts E1 and H1. Contact E2 closes to energize relay F which, over contacts F1, breaks the circuit of solenoid 17 and thereby moves the tape pinch roller out of contact with the capstan and stops the tape transport, contacts F2 close and energize solenoid 20 to rewind the tape on to spool 2, Fig. 1. Capacitor 73, Fig. 3, is charged up over contacts F3 and the capstan motor 4 is energized over contact F4. The tape then rewinds until the metallic foil on the tape, marking the start of the tape, bridges the contact members formed by the guides 10 and 11 on the tape deck, Fig. 1, thus causing relay H to pull up and self-hold over contacts H2 and B7. Contacts H1 break the circuit of relay E thereby releasing relay F and thus rearranging the circuit for forward play of the tape. The relapsing of contact F3 causes relay J to operate momentarily as capacitor 73 discharges through it and the release of contact J1 applies the reel brakes as solenoid 7 is momentarily de-energized. Relay G3 is energized via contacts H3 and via contacts G1, G2 and G3, applies the output of the replay head 9 to the line and the recorded messages are replayed to the subscriber over the line. At the end of the messages, i.e. on the occurrence of the recorded interrogation signal, relay D again operates and via contact D2 and the already closed contact H4 earths the base of transistor Q7 thus cutting off Q7 and allowing relay B to relapse and disconnect the machine from the line. Up to this point contacts B8 have maintained capacitor 47 across the- 12 V. line; with the release of relay B contacts B8 discharge capacitor 47 through relay F causing its momentary energization, contacts F2 close energizing the rewind solenoid 20 and contacts F4 close to energize motor 4 and the tape is rewound to a point just before the recording of the interrogating code signal. Again capacitor 73 is charged over contacts F3 and, when relay F releases, discharged to momentarily apply the reel brakes and leave the machine ready to answer a subsequent call. Interrogation signal recognition.-An embodiment for recognizing an interrogation signal comprising a tone of a predetermined frequency followed after a predetermined time by a tone of a second frequency comprises, Fig. 4, a frequency selective amplifier detector comprising transistor Q30 and diodes 209 and 210 the output from which causes a transistor Q31 to conduct and discharge capacitor 214 through resistor 213. The falling waveform eventually causes transistor Q32 to start to cut off. Due to the connection of transistor Q35 in a positive feedback loop over Q32 the " cut-off " of Q32 is accelerated and the differentiated negativegoing edge of the collector waveform is applied via diode 219 to trigger the monostable multivibrator comprising transistors Q33 and Q34. Thus at the collector of transistor Q33 is produced a gate opening pulse of one second duration a predetermined time after the commencement of a sustained tone of the predetermined frequency. This gate opening pulse is applied to cut-off transistor Q36 in the frequency selective amplifier formed by transistor Q35 and thus allows signals of the appropriate frequency to be applied to the detector circuit formed by diodes 236 and 237 the output from which turns on transistor Q37 and thus operates relay D to initiate the replay cycle. Transistor Q38 is provided to prevent the relay D being operated by the presence of the second tone if the first tone is maintained, thus the two tones must be consecutive and not concurrent. A transistor oscillator is shown, Fig. 5, which may be used by the subscriber to generate the signal to operate the circuit of Fig. 4, and comprises a pair of free-running multivibrators Q41, Q42 and Q44, Q45, the outputs from which feed a transducer 301 via a pair of emitter followers Q40, Q46. Multivibrator Q41, Q42 oscillates initially until the potential on capacitor 43, rises and causes transistor Q43 to conduct, meanwhile oscillator Q44, Q45 is blocked by transistor Q47 being cut off. When transistor Q43 conducts to quench multivibrator Q41, Q42, transistor Q47 conducts and allows multivibrator Q44, Q45 to oscillate; the oscillator continuing until the unit is switched off so that the output provides an audible warning that the unit is on.