The device represents a board the sizes 35x30x10mm (1.4x1.2x0.4 inc). The small sizes allow to set a board directly in the casing of a hand mike.
A basis is PT2399 chip. It is ATsP/TsAP with sampling rate 44K. Delay period minimum - 30ms, maximum - 350ms. Also on an input of the device there is a microphone amplifier on low-noise NE5532.
Works with electret and dynamic microphones without alterations of the diagram.
Technical data:
Microphone low noise amplifier with function echo