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.
The gain of this amplifier is 10 times and the excursion to the output voltage is 6.0 V (peak to...
The frequency of this circuit depends on the crystal. The transistor supports a modern equivalent. We...
This circuit uses the SQ3524, a switching integrated circuit. The circuit was found in the April...