Patent GB-445343-A (GB)
Title: Improvements in or relating to magnetic recording and reproduction of sounds
IPC: G11B5/00
Filed: 1934-08-07
Abstract: 445,343. Electromagnetic soundrecording and reproducing apparatus. BEDESCHI, G., and MONTI, G., 19, Via Arese, Milan, Italy. Aug. 7, 1934, No. 22908. Convention date, July 18, 1934. [A Specification was laid open to inspection under Sect. 91 of the Acts, Feb. 8, 1935.] [Class 40 (ii)] [See also Groups XXXIX and XL] Apparatus for magnetically recording telephonic communications (even in the absence of the called person) and for subsequently reproducing same, comprises a screw-threaded spindle 66 carrying the electromagnet 15 so that rotation of the spindle imparts longitudinal motion to the electromagnet, a contact movable with the electromagnet, additional contacts 69, 70 and 71 carried in spaced relationship on a rod 67 arranged in parallel relationship with the spindle 66, a relay 561 having its winding connected at opposite ends by wires 62, 63 to the spindle and rod respectively, a battery 56 for energizing the relay and an electric motor (not shown), which receives current from a supply line under the control of the relay and which imparts rotation to the spindle. The arrangement is such that, for placing the apparatus in a condition for recording and for shunt connecting the electromagnet through two low frequency stages with the telephone line, the relay 56<1> is energized by the battery current upon the battery circuit being closed at the contact 57 under the action of a further relay 55 excited by the telephone bell current (the switch 53 being closed) and the relay 561 is subsequently short-circuited to interrupt the recording and to disconnect the apparatus from the telephone and power lines when the contact carried by the electromagnet is momentarily brought into contact with any one of the additional contacts 69, 70 or 71. As shown, closing of the contact 57 and energization of the relay 56<1> closes the contacts 58, 59 and 60, the contact 58 locking the armature of the relay, contact 59 closing through 11 the power circuit for driving the motor whilst contact 60 closes the contacts of the telephone hook 61. The telephone line is connected at L<1>, L<2> whilst the terminals R-R of the telephonic apparatus are connected in parallel to the single changeover switch X of multiple type at the contacts 39, 38 which through the movable contacts 20<1>, 21<1> are connected to the grid of the last but one valve in the amplifier C and to the earth 51 respectively, the switch 72 being closed at 73. The output terminals 28, 29 of the amplifier are connected through the switch and by means of the contacts 75, 76 to the electromagnet 15 and loud-speaker H which are connected with one another in series. In order to reproduce the recorded communication the movable contacts 21<1>, 20<1>, 77, 78, 79 and 80 are brought into contact with the contacts 82, 81, 83, 84, 85 and 86 respectively when the terminal 76 of the electromagnet will be connected up through contact 86 to the grid of the first valve of the amplifier C and the terminal 75 will be connected to earth 51 across the contact 85. Thus, the recording is carried out with two low frequency stages and the reproduction with four stages. By moving the movable contacts of the switch into the positions 87, 88, 89, 90, 91 and 92 and closing the switch 72 at 74, signals from the radio receiving set B can be simultaneously recorded by the electromagnet 15 and reproduced in the loud-speaker H. In order to reproduce these recorded sounds, the switch X is moved into its second position. The recording may be made on cylinders or discs of steel or other magnetic material, the same electromagnet with a point of its core in sliding contact with the cylinder or disc being used both for recording and reproducing. The Specification as open to inspection under Sect. 91 comprises also a method of obliterating the recorded matter by means of a permanent magnet, a pole of which is arranged to slide on the wire, ribbon, cylinder or disc. A modified system is also described comprising an electromagnetic recording and reproducing device, a system of switches, a relay, a radio receiving set, amplifier and loud-speaker. When it is desired to record a telephone communication the switches are set so that the telephone line is connected through the amplifier to the recording device, the incoming call operating the relay to connect the driving motor of the recording device to a suitable power circuit. On cessation of the call, the relay operates to open the power circuit and stop the driving motor. By suitable adjustment of the switches, the recorded sound may be reproduced after amplification in the loudspeaker. Further adjustments of the switches allows the signals from the radio receiving set to be either recorded or directly reproduced. This subject-matter does not appear in the Specification as accepted.