This reflectometer or standing-wave ratio meter (SWR) was found in a 1980s American documentation. The diodes support general purpose equivalents.
The Schmitt optical trigger current in the dark is low. The transistors can be the BC548 and the...
This circuit is from European 90s documentation. The integrated circuit used is not very common...
Found in a 1992 book, this circuit is intended for operation with audio signals. Equivalent...