Ceramic pick up preamplifier (T1550E)

This circuit is from a 1975 RCA tube manual. The circuit appears elsewhere on this site from other sources. The supply must be between 250 and 300V.

Precision Bidirectional Current Sensor (CB5260E)
This circuit senses two-way currents serving to monitor battery charge and discharge. We find it...
Two Transistors MW Receiver (CB3976E)
This receiver was found in a 1968 publication, but can be mounted with a BC548 and BC558 in place...
Thermocouple amplifier (CB3938E)
We found this circuit in an old publication dealing with operational amplifiers. The circuit uses...