This circuit is intended for underwater communications. Of course, the critical point is the shielding to avoid water. The circuit is from an Electronic Hobbysts Handbook from the 90s.
This circuit, obtained from a 1965 magazine, can still be assembled using some modern equivalent...
We found this circuit on an Elektor from the 90s. The frequency is given by capacitor C1. The...
This powerful regulator, shown in the figure is for 5V (TTL) is suggested by Motorola and makes use...