The difference between this circuit and the previous one is that it uses PNP transistors. The circuit is from Radio Electronics magazine from July 1968. The frequency depends on R1 and C1.
We found this circuit in a 1982 documentation. An intercom to be good must be sensitive and have...
The oscillator circuit is an ICM7556, the dual CMOS version of the 555. The frequency depends on...
This simple light alarm circuit is based on the well-known 4093 integrated circuit and can be...