Don't be so ignorant. You just visited Dibrugarh once in 2006. I have been staying in Tinsukia since 1995.
Tinsukia's rake(say rake A) used to stand at platform 1 whereas the rake from DBRT(rake B) used to arrive at platform 3 hauled by loco say Loco B. This loco was decoupled from rake B and coupled to rake A whereas another loco "Loco A" got coupled to the end side of rake B, pulled the rake B in reverse direction to Dibrugarh side and pushed it back to platforn 1 of NTSK to be coupled behind rake A.
------GHY------NTSK------DBRT------...
more...
(Rake A) (idle)at platform 1
(Loco A) (idle)at platform 2
<--- (Loco B) + (Rake B) ----- (from DBRT)at platform 3
<--- (Loco B) ----- (To be coupled with rake A)from pf 3
---- (Loco B) -----> (To be coupled with rake A)at platform 1
(Loco B) + (Rake A) (Loco B attached to Rake A)at platform 1
----(Loco A)----> (To be coupled with rake B)from pf 2
<---(Loco A)----- (To be coupled with rake B)at platform 3
(Rake B) + (Loco A) (Loco A attached to Rake B)at platform 3
----(Rake B)+(Loco A)----> (reverse)(To be coupled with train at pf 1) from pf 3
<---(Rake B)+(Loco A)--- (To be coupled with train at pf 1) to pf 1
(Loco B)+(rake A)+(rake B)+(Loco A) (train with extra loco) at pf 1
---(Loco A)---> (Decoupled from train)from pf1
<---(Loco A)--- (idle)at pf 2
<---(Loco B)+(rake A)+(rake B)--- (ready to depart) at pf 1
Hope this illustration makes it clear.