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.

Logical optical driver (CB7298E)
This circuit was found in a 1968 Motorola documentation. The circuit can be implemented with...
Voltage-tuned filter (CB6938E)
This 1000: 1 voltage-controlled filter circuit was found in an Electronics Today International in a 1980s...
TPL577x Series of GaAIAs and Photo-Integrated Infrared LEDs
The Toshiba TLP577x series consists of an infrared photo-emitter (IR) and a sensor integrated circuit...