Model 2830 - 9 Line Touch-Tone Phone
This phone is sometimes referred to as a '10 button' phone; one hold button and 9 line buttons.
The phone's cable is a standard 25 pair (50 pin) male Amphenol, with unused wires
usually spared out inside the phone. Phone includes a built in ringer (rings on ~90 VAC/30Hz)
and buzzer (~18 VAC/60Hz) that have their own dedicated pairs. A small screw inside the phone
on the hookswitch lever can configure whether hanging up the phone causes the last-selected
line buttons to automatically pop-up, or remain down. A separate control box, known as a "KSU"
is needed to manage the lines, lamps, ringing and hold circuit.