Patent GB-730664-A (GB)
Title: An improved magnetic sound record transcribing apparatus
IPC: G11B25/06
Filed: 1952-10-07
Abstract: 730,664. Magnetic recording and reproducing apparatus. EDINBURGH, UNIVERSITY COURT OF THE UNIVERSITY OF, and ANTHONY, J. K. F. Dec. 24,1953 [Oct. 7, 1952], No. 25078/52. Class 40 (2). A magnetic tape sound recording apparatus has means for re-recording, from a continuously progressive section of the tape, a secondary recording on an endless band, means being provided to reproduce repeatedly at will the secondary recording. The apparatus comprises a normal type recorder and reproducer employing reeled tape as shown in the lower part of Fig. 1, and incorporates a reel preamplifier RPA, Fig. 2, and a power amplifier PA. Switching 28a, 28b, 28c, 28d, 28e, 28f is incorporated which under the control of knob 28 switches the circuits to an extreme position A for recording and to the other extreme position B for reproducing. Intermediate positions C and D are provided for " rewind " and " fast forward," respectively. Normal recording and reproducing on the reel tape only is carried out with the ganged switch 44a, 44b, 44c set to position B. During a recording operation the microphone input jacks 31, 37 are connected to the input arm 28a of amplifier RPA, and the output arm 28d connects the head RP2 via resistor R4 to the output terminal B. During a reproducing operation the head RP2 is connected to the input of pre-amplifier RPA by arm 28a and 28d, and the output via an arm 28e to power amplifier PA, to which is connected a loud-speaker at terminal 14. An H.T. supply is taken from the power amplifier PA at terminal 46 to a point 45 on reel pre, amplifier RPA and to point 43 on loop preamplifier LPA via switch arms 28b and 42b, respectively, to bias/erase oscillators, the outputs of which are connected to terminals A served by arms 28c and 42c respectively. When it is desired to make a secondary recording on an endless tape 3, shown in the upper part of Fig. 1, the switch 44a, 44b, 44c is set to position A, switch 28 to position B, and switch 29 to B. Sound is thus produced via pre-amplifier RPA and PA as for normal reproducing. The operation of switch 29 closes a D.C. circuit through switch arm 44a to terminal B of a change-over switch 40 and moves a ganged switch 42a, 42b, 42c, 42d, 42e on the loop preamplifier LPA, to position B, whereby the output from pre-amplifier RPA, via a gain control 36, is connected to the input of pre-amplifier LPA, and the output of pre-amplifler LPA connected to head RPI. The loop 3 is set in forward motion by the operation of a switch 12 to position A. When a hear back passage is heard from the loud-speaker, it will have been recorded on the loop tape 3, and the pressbutton 35 is then operated to operate a relay 47 to release switch 29 to position A and stop the reel tape 3. Switch 35 at the same time applies power to contact A of the change-over switch 40 and moves switch 42a, 42b, 42c, 42d, 42e to position B, whereby the signal picked up by head RPI is passed via arms 42d and 42a to the input of pre-amplifier LPA from the output of which the signal is passed via arm 42e to the power amplifier PA. The signal on the loop tape 3 is thus heard repeatedly until the switch 29 is returned to position B, when the switch 42a, 42b, 42c, 42d, 42e is thus returned to position A, and the drive of the reel tape 21 restored ready for a further secondary recording to be made and played back as required.