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.

KE1xF 168 MHz ARM Microcontrollers (COM129E)
November 2016 - NXP ARM Cortex microcontrollers for serial interfacing applications, NXP 32-bit...
1-Transistor Radio TR120k (CB18412E)
This simple earphone receiver was sold in the 1960s in Japan. The circuit uses a single germanium...
Rumble Filter (CB944E)
Rumble is a low frequency rumble that occurs with turntables. If the reader recovers recordings on...