"Tony944" wrote in message
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The other would be if there isn't a empty spot for an additional
double pole breaker.

No breaker will do the job he needs DPDT Manual swtich



You install a breaker to go to the generator. The lockout plate prevents
this breaker from being turned on if the main breaker going to the power
lines is on.

In effect a DPDT switch is created. The handles are just not connected.