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.

MU425S Power Supplies (COM113E)
September 2016 - Mouser Electronics is already providing power supplies for professional medical...
MOSFET Electroscope (CB1392E )
This circuit is from a 1976 documentation. It makes use of isolated gate MOSFET which is already very...
Two Transistor Adjustable Siren (CB1484E)
This circuit was published in a 1977 Radio Shack catalog. The PNP transistor may be BD135 and NPN...