Crystal oscillator with a 6A6 (T437E)

We found this circuit with the 6A6 double triode in a 1938 Radio Handbook. The power source is not provided.

Error Amplifier and Trigger Generator (CB19981E)
This circuit was found in old documentation. The components can be replaced by modern ones. The...
Active Tone Control (CB18728E)
This transistor circuit consists of a well-known bass and treble control configuration. The...
Fast Photo Darlington (CB14647E)
With the circuit shown, you can have a fast response with a Darlington configuration. The circuit is...