Elevator intercom system
KNSD-100 HONGKONG KOON TECHNOLOGY LTD

Input connections: One shielded twisted pair communication cable
(Shield should be grounded at the controller only);
Phone line requirements: Standard (analog) loop start voice grade touch-tone telephone line, PBX or key system station analog telephone line.
Optional AC adapter: 9VDC @ 200mA;
Power required: on-hook 0 ma;
Power required: off-hook 20 to 30 ma;
Phone line voltage: on-hook 24 to 56.5VDC (nominally 48VDC);
Phone line voltage: off-hook 8 to 20VDC (nominally 14VDC, min. 8 to 14VDC);
Ringing voltage: 80 to 120VAC;
Dialing: DTMF (Dual Tone Multi Frequency);
Frequency Response: 550Hz - 3400Hz, +/- 3db;
Operational Loop resistance: 600 ohms;
FCC Registration: 6HVUSA-25668-TE-T;
Ringer Equivalency Number: 0.2B.