The device is a miniature radio transmitter operating in the FM band from 88 to 108 MHz. The circuit is implemented using a single transistor that amplifies and modulates the signal from an electret microphone and transmits it over the air.
The operating frequency is determined by a coil and a tuning capacitor, which allows smooth frequency adjustment within the band by rotating the capacitor. The radio microphone is powered by a 9 V battery, providing more stable operation compared to low-voltage designs.
A wire with a length of approximately 50 cm is used as the antenna. The operating range between the radio microphone and the radio receiver is approximately 50 to 200 meters and depends on terrain, propagation conditions, and the receiver used.

Technical Specifications:
Frequency range: 88-108 MHz (FM).
Modulation type: FM.
Active component: 1 transistor.
Microphone: electret.
Frequency tuning: coil and trimmer capacitor.
Supply voltage: 9 V DC.
Antenna: wire approx. 50 cm.
Operating range: approx. 50-200 m (depending on conditions).
PCB dimensions: 42 x 18 mm.

This product is a DIY assembly kit.
It is also available as a fully assembled module - Product code 1502 (separate product).