Single Crystal Filter (CB6542E)

High selectivity filters can be obtained by combining same frequency crystals in series as shown in the circuit.

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Photocell Bridge (CB13414E)
This circuit is from a 1977 Radio Shack manual. The photocell is an LDR and the operational one is a...
High Voltage Pulser (CB6253E)
This flasher was found in an old Hands On, but uses common components. The optocoupler can be...
Neon flashlight (CB21737E)
Found in Popular Electronics from 1969, this circuit uses a neon lamp from the time that had...