Three motor tape drive mechanism

In a tape transport mechanism operable in any of several operational modes and having a d.c. forward drive motor coupled between a source of d.c. operating potential and a reference potential for driving an associated take-up reel to transport a tape coupled thereto in an arbitrarily designated forward direction and further having a d.c. rewind motor coupled between said d.c. source and said reference potential for driving an associated rewind reel to transport said tape in the opposite direction and rewind said tape onto said rewind reel, apparatus comprising:

• motor control means for selectively varying the current through said forward drive motor and said rewind motor to correspondingly vary the respective torques developed by said motors and applid to said reels,
• said motor control means including a first semiconductor device shunting said forward drive motor and a second semiconductor device interposed in series with the parallel combination of said first semiconductor device and said forward drive motor between said d.c. source and said reference potential and further including a third semiconductor device shunting said rewind motor and a fourth semiconductor device interposed in series with the parallel combination of said third semiconductor device and said rewind motor between said d.c. source and said reference potential, said first and third semiconductor devices normally conductive to respectively shunt said forward drive motor and said rewind motor with a low impedance current path during a first mode of operation so that substantially all of said current flows through said first and third transistors rather than through said forward drive and rewind motors to disable said motors;
• remote control means including transmitter means generating control signals at a location remote from said mechanism and receiver means responsive to said transmitter control signals to selectively switch said mechanism between several modes of operation,
• said receiver means comprising a plurality of remotely controlled switch devices, each of said switches being selectively enabled to produce an output signal corresponding to a particular one of the several modes of operation;
• logic control means comprising a plurality of drivers and a corresponding plurality of AND logic gate means interposed between corresponding ones of said remotely controlled switch devices and corresponding ones of said drivers to selectively enable said drivers responsive to one of said switches being enabled, each of said AND gate means having an output coupled to said corresponding driver and an input coupled to the outputs of the others of said AND gate means to prevent the enablement of said AND gate means and said corresponding driver whenever a different one of said AND gate means is already enabled;
• and
• diode switching means comprising a plurality of diodes, each of said drivers being coupled to each of said semiconductor devices by a corresponding one of said diodes,
• said enabled driver switching the corresponding ones of said diodes to conduction so as to couple said semiconductor to said reference potential to selectively vary the bias applied to said semiconductor devices and correspondingly vary the respective currents conducted therethrough.