高频振荡器由 三极管VT1和高频变压器T1等组成，是一种变压器反馈型LC振荡器。T1的初级线圈L1和电容器C1组成LC并联振荡回路，其振荡频率约200kHz，由L1的电感量和C1的电容量决定。T1的次级线圈L2作为振荡器的反馈线圈，其“C”端接振荡管VT1的基极，“D”端接VD2。由于VD2处于正向导通状态，对高频信号来说，“D”端可视为接地。在高频变压器T1中，如果“A”和“D”端分别为初、次级线圈绕线方向的首端，则从“C”端输入到振荡管VT1基极的反馈信号，能够使电路形成正反馈而产生自激高频振荡。振荡器反馈电压的大小与线圈L1、L2的匝数比有关，匝数比过小，由于反馈太弱，不容易起振，过大引起振荡波形失真，还会使金属探测器灵敏度大为降低。 振荡管VT1的偏置电路由R2和二极管VD2组成，R2为VD2的限流电阻。由于二极管正向阈值电压恒定（约0.7V），通过次级线圈L2加到VT1的基极，以得到稳定的偏置电压。

The high frequency oscillator is composed of the triode VT1 and the high frequency transformer T1. It is a kind of transformer feedback LC oscillator. The primary coil L1 of the T1 and the capacitor C1 form a LC parallel oscillation circuit with a frequency of about 200kHz, which is determined by the inductance of L1 and the capacitance of C1. The secondary coil L2 of T1 is used as the feedback coil of the oscillator, its "C" end is connected to the base of the oscillating tube VT1, and the "D" end is connected to the VD2. Because VD2 is in the forward state, the "D" end can be regarded as grounding for high frequency signal. In the high frequency transformer T1, if the "A" and "D" terminals are the first ends of the winding direction of the primary and secondary coils, the input signals from the C terminal to the feedback signal of the VT1 base electrode of the oscillating tube can make the circuit form positive feedback and generate self excited high-frequency oscillations. The magnitude of the feedback voltage of the oscillator is related to the turn ratio of the coil L1 and L2, and the turn to turn ratio is too small. Because the feedback is too weak, it is not easy to start up, causing the distortion of the oscillation waveform and the sensitivity of the metal detector greatly reduced. The bias circuit of the oscillating tube VT1 consists of R2 and diode VD2, and R2 is a current limiting resistor of VD2. Because the forward threshold voltage of the diode is constant (about 0.7V), the secondary coil L2 is added to the base of the VT1 to obtain a stable bias voltage.