Patent GB-716164-A (GB)
Title: Improvements in or relating to indicia comparison and reproducing system
IPC: G06K13/18
Filed: 1952-10-23
Abstract: 716,164. Magnetic recording and reproducing apparatus. INTERNATIONAL BUSINESS MACHINES CORPORATION. Oct. 23, 1952 [Nov. 7, 1951], No. 26604/52. Class 40 (2). In a magnetic recording and reproducing system employing two recording tracks and a common motor, means are provided for varying the time relation one with the other, so that sound from the one track may be advanced or retarded with regard to the other track. One particular use of such apparatus is described for the purpose of teaching languages, in which one track may contain speech in one language and the other a translation thereof, the time lag of the translation being adjusted to suit a listening student. In the simplest embodiment, transducing machines 1, 2, Fig. 11, are driven by a common motor 10, and the drive to a particular machine is interrupted for a period of time, depending on the time difference required, by the operation of one or other clutchdisengaging levers 30, 31. In embodiments employing a single tape carrying two tracks, the time difference is adjusted by relative movement of the transducers with regard to the tape. One method of carrying this out is to make each transducer 43, 44, Fig. 12, longitudinally adjustable by means hand screws 45, 46. Alternatively, the relative displacement of the transducers A, B, Fig. 9 (part), may be effected by passing a light of the tape over a movable pulley 63. Means are also shown, Figs. 3 and 4, in which separate tapes are marked with starting lines 35, 38, one of the tape also having additional marks each side of the starting line to indicate time delays and advancement, respectively. In another embodiment presetting may be accomplished by a time switching circuit. In Fig. 13 is shown two independent transducing machines 1, 2 coupled to a supply source 51 through independent switches 57, 58 and a common series switch 56. In parallel with the switch 56 is a time switch 52 having a cam 54 which may be manually set to open contacts 53, under the influence a spring 55, after a predetermined time. At the same time the appropriate switch 57, 58 is closed according to which machine it is desired to advance. When the contacts 53 have opened, both the switches 57, 58 are closed and the machines started in the normal way by the closure of switch 56. A time delay may be effected in either one of machines 1, 2, Fig. 14, by electronic means involving the use of cold cathode tubes 83, 83<SP>1</SP>, Driving of both machines is normally effected when the switch 64 is in the middle position. If an advance is required in machine 1, the switch 64 is tuned to the left hand position, when the power supply to machine 2 is interrupted, but a circuit to machine 1 is maintained through the contacts 92a of a relay 88, the coil of which is connected in the anode circuit of cold cathode tube 83, and through the contacts 77, 74 of the ganged part of switch 64, until, depending on the constants of resistor 85 and condenser 89, the tube 83 becomes conducting and opens the relay contacts 92a. The switch 64 is then returned to the central position for the normal drive of both machines. Similarly, if it is required to advance machine 2, the switch 64 is moved to the right hand position and operates a similar electronic circuit coupled to machine 2.