From the analysis of failure occurring on the talk circuit public parts. The aircraft intercom circuits using discrete components. According to the machine pick the drive led light, first start from the call indicator: multimeter measuring input 48V voltage from outside normal test led (light emitting diode) positive voltage to ground is very low. Visible from the circuit board, call led (light emitting diode) the cathode diode D303 for threaded, measuring diodes D303. But measuring diodes D303 cathode resistor to ground only about 10fl resistor values (identification elements in the circuit short circuit). In order to quickly determine the point of failure, disconnect step by step method is used to find it. When you disconnect the capacitor C310 (100 μl F/10V), voltage, connected to the perimeter at this time, when you call, listen to, send the voices are very large. The capacitor is the call circuit power supply filter capacitors, welding of C3lO with a multimeter measurement of the electrical barrier, and has a short circuit condition. With the same capacitor replacement, troubleshooting.