Timer for enlargers (CB8301E)

From the time when photographs developed on paper could be enlarged, this circuit was found in a 1960s General Electric documentation.

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DTMF decoder (CB17454E)
The integrated circuits used in this 1999 project are not very common today. However, they can be...
Digital thermometer with the TL505 and TL502 (CB16050E)
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200 MHz Amplifier (CB14623E)
This circuit is from the National Semiconductor FET Databook. The coil data is provided with the...