Patent GB-1413339-A (GB)
Title: Telephone-call screening apparatus
IPC: H04M1/665
Filed: 1972-11-17
Abstract: 1413339 Substation equipment J ST CLAIR KILBY 17 Nov 1972 [22 Nov 1971] 53246/72 Heading H4K In a telephone answering machine, means are provided for alerting the machine's owner in the event that a caller transmits a special signal following reception of an announcement message. If the caller decides that he does not wish to disturb the called party by transmitting the special signal, e.g. a dialled digit, he may record a message on the machine. Recording an announcement.-Mode switch Ma-Me is in position 1 and press button 36 is held down thereby providing power to regulated supply 26 which in turn activates the announcement tape's drive motor 30 and numerous circuits such as amplifier 38. A speech signal is supplied to announcement record/playback head 42 via microphone 34, amplifier 38, bias oscillator and mixer 40, and mode switch Ma. When button 36 is released, the output of tone generator 44 is then supplied to the head via closed contact 36c. The announcement tape is of the endless loop type so an "end" thereof is eventually detected by detector 32 which thereupon switches off the machine. Replaying an announcement.-Mode switch Ma-Me is in position 2 and press button 37 is held down thereby providing power to the machine. Head 42 is connected to the amplifier 38 via back contacts TRb of a transmit/receive relay TR and thence to loudspeaker 50. Answering an incoming call.-Mode switch Ma-Me is in position 3. Incoming ringing current on line 12, 13 is detected by detector 22 so as to turn-on the power and enable relay LTR which loops the line and connects it via transformer LT to the machine. The announcement is played-back to the line via back contacts TRb, amplifier 38 and back-contacts TRa. Filter 44 detects the tone which was recorded after the announcement whereby a relay TR is brought up after a delay of about one second as determined by transistorized timer 46. The caller either from pre-knowledge or as a result of information contained in the announcement may then either dial a digit, e.g. 9, or record a message. The latter reaches message head 54 via make contact TRb, amplifier 38, mixer 40 and mode switch Me3, the message tape having been started by the operation of relay TR. The machine turns off when detector EOR is triggered by the "end" of the announcement loop. If the caller dials 9, the impulses are integrated in detector 56 so as to enable transistorized relaxation oscillator 60 and a relay 58. Consequently the bleep tone on the announcement tape is applied intermittently (1 sec. on, 1 sec. off) to loudspeaker 50 thereby to alert the machine's owner. When he replies by closing hook switch contact 15, relay 62 comes up to connect the line directly to his handset 14 and to switch off the machine. Replaying recorded messages.-Mode switch Ma-Me is in position 4, thereby interconnecting head 54 with loudspeaker 50 via amplifier 38, and, playback switch 68 is operated so as to energize the tape drive motor. Fig. 4 (not shown) depicts an alternative schematic in which the answering "announcement" is constituted by a silent period following looping of the line.