The device is an electronic Emergency type siren implemented entirely with discrete components. Two transistors form a clock generator with adjustable frequency, while another two transistors are used to generate the audio signal. The output amplification is provided by a single transistor.
The siren operates from a DC supply voltage in the range of 9 to 12 V. A standard dynamic loudspeaker with an impedance of 4 to 8 OM can be used as the sound emitter.

Technical Specifications:
Circuit type: discrete components.
Generator: clock and audio generators using transistors.
Amplifier: transistor-based.
Supply voltage: 9-12 V DC.
Output: loudspeaker 4-8 OM.
PCB dimensions: 50 x 35 mm.

This product is a DIY assembly kit.