Patent GB-1504599-A (GB)
Title: Automatic control circuitry for recording tape transducing apparatus
IPC: G11B15/12
Filed: 1975-04-22
Abstract: 1504599 Tape transport control circuits L R DE BELL and D D PRICE 22 April 1975 [28 March 1975] 16613/75 Heading G5R A control circuit for a reel-to-reel recording tape apparatus has means 60 to drive the tape take-up reel (on hub 36, Fig. 1, not shown), first switching means 162, Fig. 4, or (412), (414), (416), (430), (432), (434), Fig. 8 (not shown), actuable to provide an output to energize said drive means 60 when a transistor 166, Fig. 4, or (410), Fig. 8, is rendered conductive, second switching means 170, Fig. 4, or (402), Fig. 8, operable to initiate conduction of said transistor 166 or (410), and a circuit, Fig. 5 (not shown), connected to said drive means 60 and responsive thereto to generate a voltage indicative of tape motion, said voltage being applied as a latching voltage to said transistor 166 or (410) whereby the latter is maintained conductive after said second switching means has been turned off, thereby holding the first switching means actuated and the drive means 60 energized. A tape transport, Figs. 1-3 (not shown), for magnetic tape cassettes has respective drive motors 48, 60, 72 for the supply reel hub (34), take-up reel hub (36) and captsan (68), and a motor 114 rotating a star-wheel (108) engaged by a cam follower (116) on a pivoted bar (74) carrying pinch roller (96) and magnetic head (32) so that follower (116) engages a large or small diameter portion of wheel (108) when head (32) and roller (96) are in their engaged or disengaged positions respectively, a microswitch 102 then being at position E or D respectively. When the armature of motor 60 rotates, voltage pulses are produced across resistor 292 or the brushes cross between armature segments and such pulses are detected by the tape motion sense circuit, Fig. 5, to give the latching voltage on line 308 to maintain transistor 116, and thereby coil 164 of relay 162, on after initial turn-on thereof. Start switch 170 is operative to turn on transistor 166 to energize head-engage relay 162 and cause motor 114 to engage head (32), motors 60 and 72 also being energized. Stop switch 180 is operative to turn on transistor 186 whereby transistor 166 turns off and relay 162 is de-energized resulting in drive of motor 114 to disengage the head (32), a braking transistor 194 also being turned on by switch 180. Rewind switch 196 turns on transistor 148 to energize rewind motor 48, transistor 158 acting as a latch for transistor 148 and being responsive to the latching voltage on line 308. Skip-back switch 208 turns transistor 186 on, whereby elements 166, 164, 60 are turned off, head (32) is disengaged by motor 114, and motor 48 is energized via transistor 148 to effect rewind for as long as switch 208 is held depressed. When switch 208 is released, a capacitor 234 discharges to turn on brake transistor 194 to stop reverse motion, a transistor 254 turning on when the voltage across capacitor 234 is below that across capacitor 236, whereby transistor 166 and relay coil 164 are energized again to effect head engagement and forward tape transport. Sk 7 p-forward switch 210 operates in a similar way to switch 208 but controls fast forward drive transistors 142 instead of rewind transistor 148. Fast forward switch 266 turns transistor 142 on to energize forward drive motor 60, transistor (158a), Fig. 5, acting as a latch for transistor 142 and being responsive to the latching voltage on line 308. A continuous-play switch 202a, 202b when closed together with start switch 170 effects tape playback until the end of tape is sensed by the circuit of Fig. 5, whereupon tape rewind is effected until the other tape end is sensed by this circuit resulting in a return to the forward transport tape playback state, and so on. The braking transistor 194 is turned on when release of switch 208 or 210 or operation of STOP switch 180 causes termination of rewind or fast forward wind. Transistor 194 then causes current flow through both of motors 48, 60 resulting in the tape stopping instantly and being held tight. Zener diode 260 serves to shunt transistor 194 for end-of-tape slow down. The one of motors 48, 60 which is being pulled by the other acts as a generator and when the voltage so generated exceeds the Zener level of diode 260, current flows through the generator-motor to slow it, and the tape, down. The tape motion sense circuit produces a positive latching voltage on lead 308 during normal forward or reverse tape transport, but produces a negative potential at base 178 of transistor 166 to de-energize relay 162 and stop tape transport whenever the voltage pulses from motor 60 cease or fall below a preset average threshold. This sense circuit also includes a transistor (314) controlling a stop indication light (316) and output lines (344), (346) respectively supplying tape motion pulses and a tape motion direction signal for application to an up/down tape position counter. A modified circuit, Fig. 8 (not shown), provides a transistorized switching arrangement to replace relay 162.