ON-VEHICLE RADIO COMMUNICATION EQUIPMENT AND CONNECTION JUDGING CIRCUIT

PROBLEM TO BE SOLVED: To provide on-vehicle radio communication equipment capable of correctly connecting a sense terminal for supplying a power. SOLUTION: The connection judging circuit of on-vehicle radio communication equipment is provided with a resistor R1 set between a power source VCC and a sensor terminal 22, a first voltage source V1 for adjusting a voltage from the power source VCC, a second voltage source V2 set following the first voltage source V1, a first comparator A1 for comparing the voltage of the resistor R1 with the voltage of the first voltage source V1, a second comparator A2 for comparing the voltage of the resistor R1 with the voltage of the second voltage source V2, an EXNOR circuit B1 for performing prescribed output based on the voltages to be outputted by the first comparator A1 and the second comparator A2, a PNP transistor P1 set between the resistor R1 and the sensor terminal 22, a third voltage source V3 set following the second voltage source V2, and a gm amplifier A3 for comparing the voltage of the resistor R1 with the voltage of the third voltage source V3, and for inputting currents from the PNP transistor P1.