Gordon, this was a simple intercom module for the old 1A2 key phones - it had a single common talk path for all phones, but allowed you to ring the bell or buzzer of a specific phone - the KT-37 used tone dialing and could signal 7 single digit extensions and 30 two digit extensions.
dialanumber, I couldn't find any info online for the KT-37, but did find a PDF for it's smaller brother KT-19.
goto
and enter either Melco or KT-19 in their search box to download a 3 page document.
basically, the first and last 3 pairs will be the same; for the middle 19 pairs the KT-19 used 2 wires per bell/buzzer while the KT-37 used a single wire each with all the returns connected together with "AUD GRD"
These are the connections punched down on a standard 66 block - Hope this formats OK
Tip w/bl
Ring bl/wh
LB w/o
L o/w
LG w/g
PC g/q
R40 w/br
R0 br/w
R41 w/sl
NC sl/w
R42 r/bl
R43 bl/r
R44 r/o
R1 o/r
R45 r/g
R5 g/r
R46 r/br
R6 br/r
R47 r/sl
R7 sl/r
R48 bk/bl
R8 bl/bk
R49
R9
R30
R20
R31
R21
R32
R22
R33 y/bl
R23 bl/y
R34
R24
R35
R25
R36
R26
R37
R27
R38 v/bl
R28 bl/v
R39 v/o
R29 o/v
AUD GRD v/g Common Signal Voltage 20VAC or 105VAC
AUD SUP g/v 20VAC for buzzers or 105VAC for bells sent out on "R" terminals
A GRD v/br
A BAT br/v -24VDC filtered
B GRD v/sl
B BAT sl/v -24VDC unfiltered
Haven't traced all the internal wiring, but the AUD GRD is not connected internally - think of it as a big 38 position switch with AUD SUP on the common rotor, and 37 "R" outputs