Here a link to the manual.

Panasonic KX-T7716C Quick Reference Manual

It is explained that it also requires batteries, which leaves me scratching my head.

It does explain this is indeed to be used with a PBX. This appears to be compatible with a Panasonic KX-TA824. It will probably operate with the KX-TA624 too.

The two center wires of the telset's cord are wired for ring and tip. This is why you may have dial tone upon lifting the receiver. I doubt though that all of the other features will work.

<Seems I spoke too soon, no wonder it left me scratching my head>

Last edited by DonaldR; 09/21/22 11:57 PM.

"Most people don't have a sense of humor. They think they do, but they don't." --Jonathan Winters