Enough next to your telephone to put a small plastic box, as from the speaker there is a loud voice. The secret here is simple: mounted in the box coil (scheme) “detects” the electrical signals of the phone conversation, coming then a three-stage transistor amplifier with low frequency.
Coil L1 and ULF are linked by a two-meter shielded cable. The sensitivity of the device is adjusted by potentiometer R1.
L1 contains 1250 turns of wire PEL of 0.1—0.15, is wound in several layers on a ferrite rod Ф600 (Ø 10 mm, length 140 mm). The transistors T1, T2 — МП39 — МП42, T3 — МГІ20, TP1 — output transformer from a pocket radio, Гр1 — compact loudspeaker type 0,5 GD-17, GD of 0.5-20.
Recommend to read
TO CONTROL THE MOVEMENT OF THE HAND
Before proceeding to describe the proposed design should make an important note. Developed contactless control can be applied not only in computer technology. Described constructive...
RUSTIC, COMFORTABLE
We continue to acquaint our readers — owners and garden plots — with non-traditional designs of garden furniture, and published in the Polish journal "Prob myself." Swings ...
