Voltage Level Detector (CB22135E)

We found this circuit in an English documentation from the 80's. Transistors are general-purpose types.

Bipolar Transistor Crystal Pierce Oscillator (CB13084E)
The original frequency of the Pierce Oscillator with bipolar transistor is given by the crystal, which...
Volume Expander (CB24739E)
Used in radio reception, this circuit was found in the February 1983 Radio Electronics magazine. The...
Ultrasound Blocker Filter (CB14383E)
We found this circuit in the Linear Applications Handbook of the National Semiconductor of 1994....