“LOUD” PHONE

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

  • CAPTURE THE FLAGCAPTURE THE FLAG
    On holidays, transform the homes and streets of our cities, appear illuminations, banners and flags, flags, flags... And all that is necessary to assemble, install, and then when come...
  • RC AEROBATICRC AEROBATIC
    For eight years I worked as a head of the aeromodelling circle at the station of young technicians in the city of Kiselevsk of the Kemerovo region. Himself in his spare time build a...