Patent GB-860794-A (GB)
Title: Telephone calling equipment
IPC: H04M1/276
Filed: 1958-04-28
Abstract: 860,794. Magnetic recording &c. apparatus. McGRAW EDISON CO. April 28, 1958 [May 6, 1957], No. 13357/58. Class 40 (2). [Also in Group XXXIX] A machine for recording the impulse trains of a number of subscribers, telephone numbers and for reproducing any selected one of them has means for producing a recordable signal in response to each impulse from an impulse transmitter and means to start and stop the recording process to introduce predetermined intertrain pauses on the recording. The recording is made transversely across a magnetic band driven on rollers to select the positions of individual subscribers' numbers. Machine construction.-The band 46 runs over rollers 44 and 45 and has a magnetic inner surface and an outer surface on which names may be indexed through a slot 75 in the machine casing. A finger-wheel 57 drives the drum 44 over a dog clutch 58 and has serrations engaging a detent spring 66 so that the band, driven by sprocket teeth on the drum, has a number of well-defined positions. Operation of a solenoid S during recording or playback frees the fingerwheel 57 by disengaging dog-clutch 58 through the bell-crank lever 61. The drum 45 is mounted on a rocker arm 51 biased by a spring 54 to tension the band. Extending between the sides of the band are two guide-rods 82, 83, on which slides a carriage 84 for a record-reproduce head 67 driven transversely across the band by a worm 89. Engaging the worm 89 is a pinionwheel 98 normally clutched to the carriage 84 by the friction of a wire on a pulley-wheel 100. The tension in the wire is maintained by an arm 104 on a sleeve 105 slidable along the guide-bar 82 and keyed in a slot in the guide-bar so as to rotate with it under control of a solenoid CR and its crank-arm 106. Operation of CR deflects the arm 104 to release tension on the pulley-wheel clutch wire and thereby frees the carriage for return motion under the action of a spring 114 coiled in a housing 115. When returned to its home position by spring 114 a projection 84a on the carriage 84 operates offnormal contacts. During recording and reproducing the band is pressed against the head 67 by means of a transverse pad 68, spring- mounted on a shaft 69. The pad 68 is deflected downwards to relieve the pressure when the finger-wheel clutch 58 is connected and a pin 64a on the bell-crank 61 rides on to an arm 72, and also when the relay CR deflects crank-arm 106 to effect carriage return. The worm 89 is driven from a motor 92 with a high-starting torque over universal 94 and worm gear 95 at a speed of about <SP>11</SP>/ 32  inch per second. Operation of machine.-The machine is controlled by three push-buttons; one to set the machine to record; another to restore the machine at the end of a recording; and another to initiate transmission of recorded pulses. As shown in Fig. 7 the machine may be connected up with a telephone instrument and use additional impulsing contacts 140 driven from the rim of the instruments finger wheel, or, in so far as impulses are required to make recordings, a separate impulse transmitter may be included structurally with the machine. To record a number, the button switch 122 is pressed, bringing up relay RR which locks up, lights a lamp 126, connects a 200-cycle tone source 32 to the input of a transistor amplifier 148 which is shunted by impulsing contacts 18 of the telephone instrument, and puts an open circuit in the exchange line which will not be disturbed by operation of the dial. The impulsing contacts 140 produce pulses just ahead of those from inpulsing contacts 18 and the first impulse of the first train from 140 operates a delay relay DR which locks up until the release button 123 is eventually pressed. Motor relay MR comes up with DR and is slugged to fall back 0.25 seconds after the end of each pulse train. Relay DR connects the magnetic head to the output of amplifier 148 and to  a high-frequency bias source 67a so that for each break pulse of contacts 18 a burst of 200 cycles is recorded on the magnetic band and 0.25 seconds after the last pulse of each train the motor 92 is stopped by release of MR to give an inter-train pause independent of the inter-train pauses produced by dialling. Relay DR also operates solenoid S to disconnect the finger wheel and apply the pressure-pad. After the end of the last digit train release button 123 is pushed to release relay RR which connects up a circuit to drive motor 92 over a made contact of relay DR but at the same time initiates release of DR which falls back after 0.25 second. While DR releases the 200-cycle tone source 32 is disconnected but high-frequency bias source 67a records. This is done to ensure a period of 0.5 seconds of erased recording track at the end of a complete recording to control a relay PR during reproduction. As the recording head off-normal contacts 84a are released solenoid CR energizes when DR falls back and in consequence the carriage is returned home. To transmit a subscriber's number the button 121 is pressed after the handset has been taken down and operates relay PR which connects up motor 92, locks itself up in dependence on the recorded signals reproduced over amplifier 148 with a release time of between 0.25 and 0.5 seconds, and connects the amplifier output to relay DP which responds to each recorded pulse of 200 cycles and transmits the pulses to line. At the end of the last digit train PR is confronted with 0.5 second of erased recording track and in consequence falls back, stopping the motor and connecting up solenoid CR to return the recording-head home. While PR is operated solenoid S is also energized to disconnect the finger-wheel clutch and it is to be noted that while the machine is recording or reproducing the relay circuits are such that the control buttons also are disconnected to prevent interference.