MP54 Connections

I'd like to ID and use of the connections of this LIRR MP54 at the Connecticut Trolley Museum


1/2 and 3/5 are “looped/in a cable holder”. 1 and 3 are male plug in connectors while 2 and 5 are the removable ends which are connected to the appropriate socket on the car they couple to.
All 4 point jumpers are equipped with rubber heads. All receptacles are the locking type. (LIRR info)

Thank you.

The "four point (pin) jumper" carried 650 volt DC current from the 3rd rail shoe/s throughout the train. If a train gapped or lost all its shoes, an external hand-held jumper would be plugged into a four point receptacle and held against the third rail. Close your eyes, look away!

#1/2 and #3/5 are “looped/in a cable holder”. 1 and 3 are male plug in connectors while 2 and 5 are the removable ends which are connected to the appropriate socket on the car they couple to. The high voltage traction buses, as they’re referred to, are "looped" so the open end is in a safety receptacle to keep it grounded. All 4 point jumpers are equipped with rubber heads. All receptacles are the locking type. (LIRR info)

#4 27 pin connector used for a communications trainline

#6 12 pin LV jumper??? Can anyone ID the #6 12 pin jumper use?

MP54A1 #1149 at the NY State Fairgrounds, Syracuse 9/2023


Here's the 10 pin connector:


Here's the 12 pin connector:


What is the function of the 10 and 12 pin connections? Thank you.