Hearing aid amplifier (T1580E)

This circuit is from a 1947 Radio Electronics. The 4-tube circuit is battery powered and uses a crystal phone.

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SCR neon trigger (CB8153E)
Found in a 1967 General Electric SCR manual, this circuit uses a neon lamp to produce opposing SCR...
Magnetic Microphone Preamplifier (CB16753E)
This is one of the many versions of this circuit that the reader will find on the website. This...
TTL Data Transmission (CB16024E)
The circuit shown in the figure is suggested by Texas Instruments and allows data transmission on TTL devices...