ATL Telecom OM100 User Manual

Page 15

The router connection is configured independently, so its transmit clock could either be
looped, or derived from its own internal clock source.

Of course it is not mandatory to use an external reference clock at the PDH interface, so the
above example could be equally configured to use independent timing for all channels. The
choice on whether to use the "lock clock" option, or not depends upon how the rest of the
network has been configured.

ATL USER GUIDE

OM100 Optical Multiplexer

ATL USER GUIDE
OM100 Optical Multiplexer

Notes:

1. The "lock clock" option is set on a per port basis. Any number of ports may be locked to
the timing reference on port 1, whilst other ports may be timed independently. For example,
ports 1, 2 & 3 may be locked to the timing reference, whilst port 4 remains independent.

2. On the receive side, each "locked" E1 user port derives its own timing from the incoming
E1 signal. This is re-timed to the master reference clock on port 1 before onward transmission.
This permits some flexibility within the terminating equipment. Of course the DTE must be
configured for looped timing, with its transmit clock derived from the timing it receives from
the OM100.

Example network

Notes:

There is no need for a master reference clock on the customer's equipment. However, special
attention must be paid to the clocking scheme used. The customer's equipment must either
be configured for looped timing, or to use a master clock from one of the ports (either is
acceptable). As all "locked" ports use the same clock, a master timing reference can be
derived from any of these ports.

In the above example PABX 1 has each of its two ports configured for looped timing, although
it could have been configured to use a master clock derived from port 1 (or port 2).

PABX 2 has only one user port connection. Again it is configured for looped timing.

The E1 extender can either be configured for looped timing, or operated with independent
timing.

PORT1

PORT2

PORT3

PORT4

Master unit

PORT1

PORT2

PORT3

PORT4

Slave unit

.
.
.

SDH

add

drop

mux

Reference

clock

Data

network

PABX

Router

extender

Customer’s equipment

Network equipment

OM100