Intercommunication (Intercom)
This is a great intercom circuit that can be used in many ways. It uses 22V to operate and maybe it will work at a lower voltage (you can try it). For input/output it uses a loundspeaker (20-45 Ohm) on each side.
Click to enlarge
Componets Layout
PCB
Parts List
| R1: 2,2 M | C6: 200uF/40V | |
| R2: 10 Ohm | IC1: PA234 | |
| R3,R6: 100K | LS1,2: 20-45 Ohm | |
| R4: 22K | T1: 2N3391 (BC383) | |
| R5: 1M | P1: 5K | |
| C1: 0,2uF | S1: SW-DPDT * | |
| C2: 0,02uF | ||
| C3: 0,001uF | ||
| C4: 0,05uF | ||
| C5: 100uF/40V |
*
See here how the SW should be. See also the large theoritical image.