FARTHEST ADVANCE CIRCUIT FOR A REMOTE STATION DICTATING SYSTEM

1460041 Centralised dictation systems DICTAPHONE CORP 9 Jan 1974 [10 Jan 1973] 01115/74 Heading H4K The central record/playback unit 10 of a centralised dictation system has a first switch 60 to sense the tension of a portion 62 of endless recording member 26 upstream of a record/playback head 30 and to connect, when closed, a bias voltage source 144 to enable an electronic switch 180 to implement drive of the recording member and to disable seizure control circuits in the remote dictation units 14. This prevents fresh recording over the matter backspaced to form the loop 62 and which has not been advanced to a transcribing read head 32. The transport mechanism is described in detail in copending Specification 1,456,039. Closure of cradle switch 130 at a dictating unit 14 connects a - 44 volt source 154 through conductor 12c to turn on transistor 124 thereby erasing transistor 116 to be turned on by the + 24 volt bias 144 over conductor 12b. The transistors 116, 124 "lock" on each other and turn on transistor 140 to start tape drive motors through transistor 150 and relay 168, and to provide + 24 volts on line 12c thereby preventing another unit from seizing the record/playback unit 10 and also illuminating "in use" light 140. Control of tape transport and audio circuits is effected through circuit blocks 110, 176, 178 and conductor 12a in a manner unspecified. At the end of use, opening of cradle switch 130 restores the central unit 10 to a standby condition only if the switch 60 is held open by a taut section of tape. If not, switch 60 enables transistor 180 to be turned on by the bias source 144 and resistor 160 to maintain motor drive transistor 150 conductive and to turn on transistor 186 and thereby energize solenoid 78 which engages pinch roller 36 with the tape at capstan 34 to advance the tape into loop 40 until the slack in loop 62 is taken up. A further tape tension switch 74 similarly prevents transistor 186 from operating solenoid 78 until there is slack in the posttranscription loop 54.