Because RFL™ and Hubbell® have a policy of continuous product improvement, we reserve the right to change designs and specifications without notice.
Situation:
The FRM (loss of frame) indicator on the CM4 D/I-A at Location 1 comes on. Technicians at Location
1 and Location 2 use successive loopbacks in an attempt to identify the fault as occurring in one of the
following:
1. The multiplexer at Location 1.
2. The T1 facility.
3. The multiplexer at Location 2.
Procedure: (See Figure 8-2)
1. Activate the Equipment Loopback (EqLB) in the CM4 D/I-A M-DACS multiplexer at Location
1. (It is assumed in this example that the multiplexer at Location 1 is internally timed.)
If the FRM LED remains on, then the CM4 has a fault.
Replace CM4.
If the FRM LED turns off, then the CM4 is probably fine. Proceed to Step 2.
2. Deactivate the Equipment Loopback in the CM4 at Location 1 and loopback the appropriate T1
port with an external loopback plug or a patchcord.
If the FRM LED remains on, then the DACS module or the Line I/O or the optical
Interface Adapter (OIA) has a fault.
Replace Line I/O or OIA. If the FRM LED remains on, then replace DACS
module
If the FRM LED turns off, then the DACS module or the Line I/O or the optical
OIA is probably fine. Proceed to Step 3.
3. Remove loopback plug or patchcord at multiplexer Location 1. The FRM indicator should turn
on again. Activate the Line Loopback in the CM4 D/I-A M-DACS multiplexer at Location 2.
If the FRM indicator remains on at Location 1, then the T1 facility or the DACS module at
Location 2 is probably the source of the fault.
Loopback T1 facility. If the FRM LED turns off, then replace DACS module
If the FRM indicator remains on, then the T1 facility and the DACS module is
probably all right, leaving the CM4 D/I-A at Location 2 as the likely source of the
fault.
M-DACS-T1 RFL Electronics Inc.
October 25, 2004 8-5 (973) 334-3100
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