AFAIK , It is known as Multiple Unit and commonly phrased as MUed Locos. They are connected via communication cables provided on each side of the locos. The main control unit in the leading loco controlled by LP , controls the CU of the following loco. What ever command the LP gives to the main loco, are transferred/communicated to the CU of the following loco via the connected COMM cables, i.e acceleration , brake etc. And hence they are synchronized. Hence only 1 LP and 1 ALP is required in the leading loco. We generally get to see MUed locos as they bring heavy loaded BOXN rakes here. If anyone has more to explain, please share.
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