With four components, and the on:off switch, Bill K9HZ provides the ultimate reverse voltage and over-current protection system for your µBITx. The fuse protects the circuit from excessive current draw – so you won’t blow your finals when you wind up the bias too far and they try to go into thermal runaway. The relay must be powered on to power your µBITx (and the switch must be turned on). With the series diode in place the relay cannot turn on unless the power is wired up correctly.
The All-band HF Amateur Radio Transceiver: Just waiting to be modified