External Timing Ports

Note: This section applies to ERX-7xx and ERX-14xx models only. The ERX-310 router does not support external timing.

The SRP I/O module has two input ports for external clock sources. These ports provide a way to ensure that the router system clock remains synchronized with the network's system clock. The primary clock is labeled A; the secondary, redundant clock is labeled B.

Use the connectors appropriate for your locale (European or North American standard):

• European—Two 75-ohm E1 2.048-Mbps inputs with BNC connectors
• North American—Two 100-ohm T1 inputs with three pin wire-wrap connectors. Pins are labeled T (tip), G (ground), and R (ring). We recommend using 26-AWG wire minimum.

  Note: Use shielded cables to connect the external clock sources to the clock source input ports.

  Figure 24: SRP I/O Module for ERX-14xx Models

  

To connect the clock source input ports:

1. Depending on the connector type, complete one of the following tasks:
   • E1: Attach the BNC connector to Clock A's external timing port.
   • T1: Wrap the tip wire on pin marked T of Clock A's external timing port, the ground wire on G pin, and the ring wire on R pin.

     Note: You can use a wire-wrap gun to attach wires to pins.

2. Attach the opposite end of the external timing cable or wires to your network's clock source A.
3. Repeat Steps 1 and 2 for the Clock B connections.

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