This circuit was found in a 80’s American documentation. The adjustment trimpot is from 47k to 100k. The diodes are general-purpose types use and the supply voltage depends on the relay.
In the figure we have the typical configuration of a voltage regulator based on an operational amplifier....
Found in 1969 Ferranti documentation, this small font is characterized by its low ripple....
We found this circuit in a 1980s publication on telephony. The circuit uses an integrated...