This QST circuit generates 4 frequency signals according to the crystals used. Transistors admit equivalents although the indicated types can still be found with some ease.
Here is an interesting project for those who own a pool and are afraid that someone will fall into...
This circuit is from the old RCA transistors manual of 1964. The transistor can be the BC558 and...
Using a new Maxim integrated circuit (www.maxim-ic.com) the amplifier shown in the figure can be...