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Each phone in a Summit 80 system I'm working with has a "(T)" at the top line, right side of the LCD display?

Could it be a (T)one ring or (V)oice Announce indicator?

All of the VU-9208 phones have this, haven't checked the larger system phones yet.

Any thoughts?
That's exactly what it is. The phones are in tone ringing mode for intercom calls. You can press the TRANS/PGM button and dial 131 to change the intercom call arrival mode on the phones.
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