How to Perform Bidirectional E1/T1 Monitoring? Balanced RJ48 Y-Cable Wiring

Often mistakenly referred as "RJ45", the modular registered jack (RJ) connectors for balanced 120Ω E1 and T1 interfaces, on VeEX products, are based on the standard RJ48 wiring on an 8-position, 8-conductor (8P8C) modular connector.

Refer to the What is the pinout for the balanced RJ48C article for more details.

Bidirectional E1/T1 Monitor (RJ48M)

For bidirectional monitoring applications, the modular connector on certain VeEX test sets adopt the RJ48M pinout, adding pins for a secondary receiver. This allows test sets, configured in High Impedance (Hi-Z or Bridge) mode, to tap the link and monitor both directions of a T1 or E1. Such application requires a custom-made Y-Cable.

RJ48M Pinout

Pin 1: Rx1- (A/Ring)
Pin 2: Rx1+ (B/Tip)
Pin 3: No connection
Pin 4: Tx1- (A/Ring)
Pin 5: Tx1+ (B/Tip)
Pin 6: No connection
Pin 7: Rx2- (A/Ring)
Pin 8: Rx2+ (B/Tip)

E1/T1 Monitor Y-Cable Wiring

VeEX does not offer an E1/T1 RJ48 Monitoring Y-Cable, however it is quite easy to build one based on the wiring details below.

Here is a suggested implementation of the Y-Cable

How to Perform Bidirectional E1/T1 Monitoring? Balanced RJ48 Y-Cable Wiring

For balanced E1 and T1 applications, VeEX's test sets follow the RJ48C pinout and wiring for terminated (120Ω) applications. For high-impedance bidirectional monitoring applications, certain test sets offer a Monitor mode with dual receivers in an RJ48M pinout

Bidirectional E1/T1 Monitor (RJ48M)

RJ48M Pinout

E1/T1 Monitor Y-Cable Wiring

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