Status detector fault detector

Three diodes on the input of a fault detector are coupled to the output of a status detector driver to clamp the output of the status detector driver positive with respect to ground. A fault detector amplifier is coupled to the diodes through a resistor and capacitor filter to eliminate transients. The amplifier normally produces a low output signal. This low signal back biases a diode at the input of the status detector driver and a second diode at the input of an error signal producing circuit. The error signal producing circuit comprises a normally on transistor. A foreign potential at the output of the status detector driver is detected by the fault detector amplifier which will then produce a high output signal. This will forward bias the diode in the status detector driver circuit turning the status detector driver circuit off, and also turning off the transistor in the signal producing circuit to produce an error signal. Resistors are included in series with the sense point matrix diodes to protect them from a high current. Diodes are provided at the input of the receiver to also protect the receiver from foreign potentials.