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.

Telephone Dialer (CB5979E)
This circuit is from the 80's, using an integrated of the time. The circuit serves as a reference,...
AC to DC Converter (CB5098E)
This circuit was obtained from an American 80's documentation. The operational ones can be...
741 Logarithmic Amplifier (CB25723E)
This logarithmic gain operating configuration was found in the June 1994 Electronics Now magazine. The...