We found this circuit in Radio Electronics from the 90s. The components are current. The sensor is a common general-purpose transistor. The connection to the sensor is made by twisted pair.
This circuit is found in an American documentation from the 80's. The circuit measures the power of...
This circuit is the equivalent of the CB121, but is triggered with the negative transition of the...
We found this circuit in a 1996 publication. Equivalent components can be tried, especially in the...