There was a "Know" issue with some R.7's where the processor would have a green light but all ext's would be dead.
I thought it was just a certain S/N span of R.7's.

But anyhow, if you have the stand-a-lone control unit plugged into know good A/C power and you plug a know good 2pr cord from control unit to phone,........ then yeah, your ACS is bad.

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