sundance-communications.com/forum Forums Wiring - Telecom Carriers - Trunks & Services T1's, CSU's and DSU's 4 wire T1 wiring question

First of all I would like to say how GREAT it is to have a site like this one. I work for a VERY large telecom and it almost a disgrace the lack of training they offer for such a highly technical job. My question is this: In a Central Office, On a 4 wire circuit you have T,R,T1 and R1. These have been explained to me as tip, ring, tip1 and ring1, but are they really transmit, receive, transmit1 and receive1? I know that if you are wiring up equipment to equipment ( channel bank to channel bank)you have to roll the jumpers. Otherwise you have xmit to xmit and recv to recv. Any information would be greatly appreciated.

Actually, T&R are one pair for one direction, and T1&R1 are a second pair for the other direction. It is still "Tip" and "Ring", not "Transmit" and "Receive".

In the "old Days" T1 & R1 were the battery side of the ckt ie dial tone ect; and the T & R were the load or condenser side of the ckt ie tel. set, ect. So when I was in the 4 wire crew we used T1-R1 as the xmt side T&R as the rec. from the distant end. But now adays anything can be whatever.

Normally, on a 4-wire circuit, the "word doc" (may be called differently where you are) will specify which pair is transmit and which one is receive.

All you have to do is wire them accordingly.

As previously stated, T&R is one side of the circuit (tip and ring) while T1&R1 is the other.

Even if you were to reverse them, it can still be corrected in the field - been there and done that many a times - so it's not the end of the world.

Thanks everyone for the explanation, I appreciate them !!!!!

"I work for a VERY large telecom and it almost a disgrace the lack of training they offer for such a highly technical job."

No my friend it is a TOTAL disgrace!

You transmit on T,R sometimes called XT,XR and Jim receives on T,R in the field. Jim transmits on T1,R1 You recieve on T1,R1 sometimes called RT,RR. It can be a little confusing at times.

Remember the golden rule for CO technicians:

Allways wire the CO straight. Never turn the wiring over to fix a problem unless you have wired it incorrectly to begin with. Since the outside facilities are more phrone to turn overs and reversals, insuring your wiring is straight eliminates a potential point of failure.

Unless otherwise indicated in an equipment print. The TR represent the transmit "IN" to the equipment, and the T1R1 is the Receive "OUT" from the equipment. Standard transmission convention for all WeCO/Lucent channel bank equipment, such as D4's.

However with Digital Loop Carriers (DLC's AKA: SLC's) instead of a TR/T1R1 frame block designation, the associated PG cable pairs function with an equivalent assignment relative to the IN/OUT of the channel units. TR = ODD cable Pair/BP. T1R1 = Even cable Pair/BP. PG cable pair or BP 01 is the INPUT to a 4W DLC channel unit. PG cable pair or BP 02 is the OUTPUT from a 4W DLC channel unit.

As a follow up. When wiring back to back carrier 4W DS0 Special Service channel units, the wiring scheme will be:

FAC 1 TR to FAC 2 T1R1/FAC 1 T1R1 to FAC 2 TR.
With 4W D4 and DLC, D4 T1R1 to DLC ODD pair assignment/D4 TR to DLC EVEN pair assignment.

The field will wire NCTE to the PG Cable BP assignment in a similar fashion: ODD BP signal IN/EVEN BP signal OUT.

If 4W DLC in the CO, and 2W DLC in the field, the field tech only wires the ODD BP assignment.

NOTE: LiteSpan E&M channel units are not Dual Channel tyoes, and only support a single DS0 channel. Odd Pair is TR, Even Pair is T1R1, next higher ODD pair are the E & SG leads, and the next higher EVEN pair are the M & SB leads to support Type-I/II E&M signaling applications.