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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Low battery indicator (CB21619E)
Based on an Analog Devices LTC1540, this circuit consumes only 50 uA, serving to monitor the...
Field strength meter (CB6234E)
This circuit was found in a 1980s documentation. The diodes may be general purpose diodes such as 1N34...
24 Hour Multi Timer (CB16773E)
We found this digital timer circuit in a 1994 publication. The power is supplied by 12 V, which is the...