Circuit card present sense and protective power supply inhibit for airborne application of ATM switch unit

A system for delivering power to a circuit card only when the circuit is coupled to a power control circuit, said system comprising:

• a circuit card connector terminal mounted on said circuit card;
• an opposite mating connector terminal corresponding to said circuit card connector terminal, said opposite mating connector terminal coupled to said power control circuit, said power control circuit configured to detect whether said circuit card connector terminal is coupled to said opposite mating connector and to generate a first card present signal;
• a logic circuit in said power control circuit which generates a power supply enable signal based on the first card present signal;
• and,
• a main power supply which provides power to said circuit card, said main power supply configured to receive the power supply enable signal from said power control circuit and to provide power to said circuit card only when the power supply enable indicates that the circuit card connector terminal is coupled to said opposite mating connector.

A system for determining when to provide power to a circuit card in a transportation vehicle ATM switching system comprising:

• a circuit card connector coupled to the circuit card, said circuit card connector including a contact which connects a sense pin directly to ground;
• a power control circuit including a control circuit connector having a contact to said sense pin, said sense pin coupling said power control circuit connector to said circuit card connector;
• an auxiliary power supply providing a voltage to said contact to a sense pin;
• a logic circuit which monitors said contact to a sense pin to determine whether said circuit card is coupled to said power control circuit;
• and,
• a power supply providing power to the transportation vehicle ATM switching system, the power supply configured to receive the output of said logic circuit and to provide power to said circuit card only when said circuit card is coupled to said power control circuit.