We found this circuit in a 1967 American documentation. It is a transmitter for animal research, monitoring intestinal pressure. The operating frequency is 22 kHz.
This alarm, from a 1996 magazine, can be fitted with two BC548s in the original configuration...
Using only one general purpose transistor this circuit is powered by batteries. The lamp of the...
Can be used as a shield, this old American documentation circuit offers digitally selected...