This circuit is from an old Mullard (Philips) manual with applications using the 555. Choosing appropriately the resistors and the timing capacitors, the ranges obtained can exceed days.
This circuit applies to an old dial phone by detecting light pulses in the dial. The circuit is...
This circuit conditions an audio signal, acting as a filter, control, and reaper of signals. The...
Found in old documentation, this timer uses a sensitive relay and a 2N2646. The time is given by...