[Elecraft] KPA500 / KAT500 and W2 watt meter question

[Andy Durbin]

"In the KAT500 manual, page 5, Figure 1 Cabling Diagram, is the better and safer way to configure the system.  NO key line interrupter is needed.

How does an Elecraft station that controls KPA500 and KAT500 using AUX cables inhibit keying when a SteppIR antenna is moving the tapes?  This protection must be provided or element tapes and brushes can be damaged.

Andy, k3wyc