Chapter 4 Troubleshooting and Diagnostics IPmux-1/1E Installation and Operation Manual
4-8 Performance Monitoring and Troubleshooting Statistics
Table 4-3. E1/T1 Alarms Alarm Description
LOS A Loss of Signal indicates that there is either no signal arriving from the adjacent E1/T1 device or no valid E1 voltage mask or no voltage alteration between
positive and negative amplitudes.
For E1 links, the LOS counter will increase by one for each second during which a consecutive 255 pulses have no pulse of negative or positive polarity.
For T1 links, the LOS counter will increase by one for each second during which a consecutive 192 pulses have no pulse of negative or positive polarity.
A LOS alarm can also be noticeable when the front panel Sync LED is off (Green indicates Synch is on).
Recommendations:
Check the physical layer (connectors, cables, etc.)
LOF (Red) A Loss of Frame indicates that the IPmux lost E1/T1 synch opposite its adjacent E1/T1 device.
In more detail, this is a period of 2.5 seconds for T1 or 100 msec for E1, during which an OOF (Out Of Frame) error persisted and no AIS errors were detected.
For E1 links an OOF defect is declared when three consecutive frame alignment signals have been received with an error.
For T1 links, an OOF defect is declared when the receiver detects two or more framing errors within a three msec period for ESF signals and 0.75 msec for D4
signals, or two or more errors out of five or fewer consecutive framing-bits.
A LOF alarm can also be noticeable when the front panel Sync LED is off.
When the IPmux enters a Red alarm condition, it sends an Yf bit (Yellow alarm or RAI) towards the adjacent E1/T1 device.
Recommendations:
Check all framing related parameters (CRC-4, CAS enabled/disabled, ESF/D4 (for T1), etc.), and physical connections.