Using transistors at the time, this circuit was found in a 1967 Ferranti documentation. The circuit is for 150-ohm transmission lines.
This circuit is from an old American documentation, from 1977, but it can be implemented with more...
This circuit was found in a 1970s American documentation. It can be applied to almost any...
This circuit generates an accurate 1 Hz signal controlled by a crystal. The circuit is from 1995...