Computer controlled file protect

Claim 1

IN A COMPUTER SYSTEM INCLUDING A MAGNETIC TAPE UNIT HAVING A CARTRIDGE FOR CARRYING A MAGNETIC TAPE THEREIN AND A TAPE TRANSPORT FOR RECEIVING SAID CARTRIDGE, AN ERASE CIRCUIT FOR COACTIONW ITH SAID MAGNETIC TAPE, A TWO POSITION ERASE CIRCUIT CONTROL SWITCH MOUNTED ON SAID TRANSPORT FOR CONTROLLING THE COMMISSIONING OF SAID ERASE CIRCUIT IN A FIRST POSITION AND THE DECOMMISSIONING OF SAID ERASE CIRCUIT IN A SECOND POSITION, A TWO POSITION SWITCH CONTROLLER MOUNTED ON SAID CARTRIDGE IN OPERATING RELATION TO SAID CONTROL SWITCH WHEREBY WHEN SAID CONTROLLER IS IN A FIRST POSITION SAID CONTROL SWITCH IS IN ITS FIRST POSITION AND WHEN SAID CONTROLLER IS IN ITS SECOND POSITION SAID CONTROL SWITCH IS IN ITS SECOND POSITION, A SOLENOID INCLUDING AN ACTUATOR MOUNTED ON SAID TRANSPORT, SAID ACTUATOR BEING IN A POSITION TO OPERATE SAID CONTROLLER TO CHANGE THE POSITION OF SAID CONTROL SWITCH WHEN SAID SOLENOID IS ENERGIZED, AND MEANS UNDER CONTROL OF SAID COMPUTER FOR ENERGIZED SAID SOLENOID.