For those interested, it acts mostly as a high speed relay between the 
transceiver and the amplifier, while at the same time, the way I understand 
it, it also protects the transceiver from voltage spikes, thus overloading 
the transistors in the rig.  People not using it, often complain of their 
solid state amp automatically tripping off during transmissions.  So, in 
short, and maybe someone can explain it better, it is a high speed 
protection relay between the amp and the radio which prevents those small 
electrical arks from occurring when a relay closes contact during a 
transmission key on, key off, action.

Phil.
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