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.

INA260 Digital Current and Power Monitor
March 2017 – Mouser Electronics already has the new Texas Instruments INA260 digital current and...
8bit Digital to Analog Converter (CB5169E)
This circuit was found in an ancient American documentation. The components of the time are not...
8 Bit DA Converter (CB5171E)
This circuit of the 80's makes use of components of the time. The circuit is from an American...