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.

555 Linear Ramp Generator (CB24462E)
We have other similar setups on this site. This one is from September 1976 Radio Electronics. The...
24 V Power Control (CB839E)
This low voltage AC control uses a triac. Any TIC series triac can be used and this device must be...
540 mW amplifier (CB21801E)
Using germanium transistors, this amplifier provides a 540mW output power when powered by 9V. We...