The idea behind this project is a protection brick, that can be added anywhere, that will provide RF Over-Voltage /Over-Current protection to whatever is attached to the output side. It is possible I will add some lightning protection in the form of your typical gas-discharge cartridge-BUT  I think that is better done by an Alpha-Delta device closest to where the antenna comes into the facility. So it is presumed that such protection precedes this device, as a general principle.

This can  be done with expensive vacuum relays-such as the RJ1-A, but the idea here is to provide just protective switching, fast enough to be useful (< 20ms), activated by either RF or DC switching, that doesn't have to carry significant RF, but can standoff just about anything to be encountered in normal ham radio conditions.

Design specifications for the particular (over the counter) reed switch I'm using are: 1000V standoff voltage; 2A carry current, non-switching; 20W carry power (which for a receiver protection device is more than sufficient.)

The principle idea here is stated in the block in the lower left corner of the drawing. Basically, if ANY of several conditions exist, the 'brick' will be OPEN, and not pass RF any further. Those conditions include: 1) No Power; 2) 'EVENT' detection at any of its several inputs: a) Significant (e.g. transmitter-and possibly nearby lightning) RF at the RF-Input; or, b) An 'EVENT' at any of the operating inputs, e.g. key, PTT, or the passed-through EVENT-Detect line going active from some other unit (for example a footswitch intended to switch to transmit, a similar panel switch for TUNE, etc.)

All of these EVENTs are active-LOW, and set the unit into its BYPASS mode, protecting the connected device (receiver or, in my case, a receiver distribution unit.) I have included opto-isolation for EVERY data line, both incoming and outgoing. There is also included a specific line to input the primary station keying, and an output line to pass it along. I will probably change the output keying to another reed relay, to simplify POS and NEG keying in changing from a modern transistorized rig to one of my BoatAnchor rigs. I MAY keep it solid state, and use different POS and NEG outputs.

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