Drain detector. The antenna goes to pin 3 of the antenna coil P-C70-A. Pin 4 goes to circuit ground and earth ground. Pin 2 of the coil is also grounded while pin 1 connects to the stator of the variable capacitor. The rotor is grounded. Pin 2 of the coil also goes to the gate of the FET, M P F 102. The source goes through a 22 k ohm resistor to ground. The source also connects to the positive end of a 1 microfarad 25 volt capacitor. The negative end of the cap is grounded. The drain goes through a 10 k ohm resistor to plus 12 volts. The drain also goes through a 100 pf cap to ground. The drain also goes to the positive end of another 1 mike 25 v cap. The negative end goes to the center contact of the output jack. The shield contact is grounded. A drawing identifies the leads of the F E T. With the leads facing you and the flat side up the leads are, from left to right, drain, source, and gate. End verbal description.