Direct relay photo control (CB8332E)

This two-component circuit is from a 1967 Philips documentation. The relay is a high-sensitivity type with 24 V operating voltage and 1,000 ohm coil.

VLF to VHF active antenna (CB6980E)
Found in a European magazine from the 1980s, this circuit can amplify signals from 10 kHz up to...
Proximity Voltage Indicator (CB4645E)
This circuit indicates whether a cable or wire is energized by simply approaching its antenna. The...
Medical instrumentation preamplifier (CB7235E)
Suggested by Intersil in documentation from the 90's, this circuit is valid for modern operating...