Control circuit for a bidirectional recorder

Claim 2

A control system for deactivating a recording bias oscillator circuit of a bidirectional recorder prior to activating a reverse solenoid for reversing the motion of tape in said recorder and for switching a recording head, comprising means for sensing the motion of the tape in the recorder and providing a signal when said motion is reduced below a predetermined speed, first switching circuit means responsive to said signal for deactivating the recording bias oscillator circuit, and second switching circuit means responsive to said signal connected for actuating said reverse solenoid, said second switching means including a delay circuit for delaying the operation of said second switching means for a predetermined time after the actuation of said first switching means, whereby the recording bias oscillator circuit is deactivated prior to the switching of said head.

Claim 3

A control system in accordance with claim 1 in which the recorder includes an audio circuit and the first switching circuit means deactivates said audio circuit.

Claim 4

A control system in accordance with claim 2 in which the recorder is a cassette changer and the second switching circuit means pulses said solenoid in response to said signal.

Claim 5

A control system in accordance with claim 1 in which means are provided for supplying a positive voltage, the motion sensing means includes a cylinder rotated by movement of said tape, said cylinder having alternate segments on its surface of conductive and nonconductive material and a conductive circumferential band connecting said conductive segments together, a first sliding contact on said band, and second and third sliding contacts circumferentially disposed on said cylinder so as to be alternately connected by said conductive segments to said first contact, a capacitor connected between ground and said first contact, said third contact being connected to ground, the second switching circuit means includes a resistor and a capacitor connected in series between said positive voltage means and ground, a steering diode having its positive terminal connected to the junction between said resistor and said capacitor and its negative terminal connected to said second contact, a first Schmitt trigger circuit connected to the junction between said resistor and said capacitor so that said trigger circuit switches states when the voltage across said capacitor reaches a predetermined level, a switching transistor having its collector-emitter circuit connected in series with said reversing solenoid and said positive voltage means, the output of said first Schmitt trigger circuit being connected to the base of said switching transistor, the collector of said switching transistor being connected through a steering diode and a resistor to the junction between said resistor and said capacitor, the junction of said resistor and said capacitor being connected to ground through a switch.

Claim 6

A control system in accordance with claim 4 in which the first switching circuit means includes a resistor and a capacitor connected between the positive voltage means and ground, the junction between said resistor and said capacitor being connected to said second contact, a second Schmitt trigger circuit connected to the junction between said resistor and said capacitor and being biased so as to switch to its second state when the voltage across said capacitor reaches a predetermined level, and a switching transistor having its collector-emitter circuit connected in series with said audio circuit, said recording bias oscillator circuit and said positive voltage supply, the output of said second Schmitt trigger circuit being connected to said switching transistor so as to render said switching transistor nonconductive when said second Schmitt trigger circuit is in its second state of operation.