Apache Point Observatory uses custom Telco cables to connect harmonicas (a set of 8 RJ-11 jacks connected to a male telco connector) and/or patch panels (multiple harmonicas mounted in a panel) together. The wiring was chosen so that RS-232 transmit and receive are twisted with their respective ground, and the two handshake lines are twisted together. Note that APO uses USOC-wired harmonicas and patch panels with sets of eight 6-wire 6-position RJ11 jacks (this is one of several standard types).
The cable uses female telco connectors. This is the opposite of typical phone cables, and is intended to reduce mix-ups.
pin color pin color 01 Blue/White 26 White/Orange 02 Orange/White 27 White/Blue 03 Green/White 28 White/Green 04 Brown/White 29 White/Gray 05 Gray/White 30 White/Brown 06 Blue/Red 31 Red/Blue 07 Orange/Red 32 Red/Green 08 Green/Red 33 Red/Orange 09 Brown/Red 34 Red/Brown 10 Gray/Red 35 Black/Blue 11 Blue/Black 36 Red/Gray 12 Orange/Black 37 Black/Orange 13 Green/Black 38 Black/Brown 14 Brown/Black 39 Black/Green 15 Gray/Black 40 Black/Gray 16 Blue/Yellow 41 Yellow/Orange 17 Orange/Yellow 42 Yellow/Blue 18 Green/Yellow 43 Yellow/Green 19 Brown/Yellow 44 Yellow/Gray 20 Gray/Yellow 45 Yellow/Brown 21 Blue/Purple 46 Purple/Blue 22 Orange/Purple 47 Purple/Green 23 Green/Purple 48 Purple/Orange 24 Brown/Purple 49 Purple/Brown 25 Gray/Purple 50 Purple/Gray
pin color pin color 01 White/Orange 26 Blue/White 02 White/Blue 27 Orange/White 03 White/Green 28 Green/White 04 White/Gray 29 Brown/White 05 White/Brown 30 Gray/White 06 Red/Blue 31 Blue/Red 07 Red/Green 32 Orange/Red 08 Red/Orange 33 Green/Red 09 Red/Brown 34 Brown/Red 10 Black/Blue 35 Gray/Red 11 Red/Gray 36 Blue/Black 12 Black/Orange 37 Orange/Black 13 Black/Brown 38 Green/Black 14 Black/Green 39 Brown/Black 15 Black/Gray 40 Gray/Black 16 Yellow/Orange 41 Blue/Yellow 17 Yellow/Blue 42 Orange/Yellow 18 Yellow/Green 43 Green/Yellow 19 Yellow/Gray 44 Brown/Yellow 20 Yellow/Brown 45 Gray/Yellow 21 Purple/Blue 46 Blue/Purple 22 Purple/Green 47 Orange/Purple 23 Purple/Orange 48 Green/Purple 24 Purple/Brown 49 Brown/Purple 25 Purple/Gray 50 Gray/Purple
