Patent GB-865014-A (GB)
Title: Remote dictation system
IPC: H04M11/10
Filed: 1958-03-25
Abstract: 865,014. Centralized dictation systems. DICTAPHONE CORPORATION. March 25, 1958 [March 28, 1957], No. 9570/58. Class 40 (4). A remotely operated dictation system comprises a centrally located recording and control apparatus, a plurality of remote dictators' instruments each including a microphone, a communication circuit including first and second lines for connecting the microphones to the recording and control apparatus, first and second relays connected in series with power supply means between the first and second lines to be operated by the current flow in the first and second lines, control means at each of the dictators' instruments for selectively establishing two different current conditions in the first and second lines, the first and second relays being selectively actuable by the two current conditions respectively, and operating means under the control of the first and second relays to establish predetermined control functions at the recording and control apparatus in accordance with the setting of the control means. In some respects the system is similar to that described in Specification 811,561. In the drawings, Fig. 1 is a circuit diagram of one embodiment of the system, the circuit of a dictator's substation 10 being shown in Fig. 2. All relays are shown unoperated, but relay 110 is normally operated when the dictating machine 20 is available for use. When a dictator lifts his handset, his cradle switch 46 completes a D.C. circuit over speech wires 12 and 14 and the windings of relays 50 and 54, which are arranged to operate at different current levels. Resistor 30 keeps the steady-state current in this circuit too low to operate either of the relays but high enough to hold relay 50 when it is already operated. (The two relays 50 and 54 have identical windings and are balanced symmetrically about the power supply 52 in order to minimize stray electrical pick-up in the speech circuit 12, 14.) The initial surge of current through a capacitative path 64, 66 in parallel with resistor 30 brings up line relay 50, followed by " in-use " relay 70 and " hold " relay 86. This starts the A.C. motor 92 of the dictating machine 20 and also feeds D.C. to. leads 16 and 18, lighting a lamp 154 at each substation and operating the privacy relays 28 at all the substations not in use. (The output of the D.C. supply 146 includes a component of 120 cycle hum which is heard by any dictator who subsequently lifts his handset while the system is in use.) The dictator then operates his switch 60 which shortcircuits resistor 30 to raise the level of D.C. in the speech circuit 12, 14. " Record " relay 54 operates, followed by " clutch " relay 102 which completes a circuit for solenoid 106, thereby actuating clutch 94 so that the motor 92 drives the recorder. Recording proceeds in normal fashion. To make an " end-of-letter " mark on pad 190, the dictator operates a spring-loaded switch 22, momentarily breaking the speech circuit 12, 14. Relays 50 and 54 fall back, followed after a delay by relay 70. This energizes marking solenoid 184 and brings up relay 198 to maintain a circuit for the clutch solenoid 106, so that the marking device 186 is driven by the clutch 94. The " hold " relay 86 has a release time of several seconds, so that the circuit is remade before it falls back and the dictator keeps control of the machine. The dictator may signal to the machine attendant by means of switch 38 (as described in Specification 811,561) to put the machine in " reproduce " condition. Control lever 204 then closes switch 206, and, if the dictator hangs up with the machine in this condition, relay 110 is shunted and released, feeding D.C. (including hum) to leads 16 and 18 to operate all the privacy relays. Relay 220 operates, activating a tone generator 224 which sends a signal to the attendant by way of a loud-speaker 214. " Playback " and " correction " switches 234 and 236, respectively, are provided, as described in Specification 811,561. When either of these is operated, hum fed from leads 16 and 18 to receiver 158 is minimized by correct setting of a potentiometer 242.