Wh/Bl -1 Tip
Bl/W - 1 Ring
W/O - 1A
O/W - A1
W/Gn - LG
Gn/W - 1 Lamp

W/Br - 2 T
Br/W - 2 R
W/SL - 2A
SL/W - A1
R/BL - LG
BL/R - 2L

R/O pair - 3 T/R
R/Gn pr - 3A/A1
R/Br pr - 3 LG/L

R/SL pr - 4 T/r
Bk/BL pr - 4A/A1
Bk/O pr - 4 LG/L

BK/Gn pr - 5 T/R
Bk/ Bn pr - 5 A/A1
Bk/SL pr - 5 LG/L

Y/BL or Y/O pr - usually assigned to the buzzer for Intercoms

Y/Gn pr - Often assigned as a Lamp for the Hold button (Misc. features)

Y/SL pr - always assigned for the Ringer wired for the "Common Bell"

The Violet group was usually set aside for speakerphone leads. On some sets (2564 series) there was only a 16 pair cable (if I remember correctly) and the violets, all the A1s but the first one and some other leads (Some LGs maybe?) were missing completely.

And no, without a KSU you would need a separate ringer for each line.

Also the correct term is a "Key Telephone" or a "Key Set" a KTU is actually a "Key Telephone Unit" - which is a circuit board that plugs into a KSU (Key Service Unit) - the things that make key telephones work.

Sam

"Where are we going and why are we in this hand basket?"