August 2001
Beginner
304 pages
10h 3m
English
Content preview from T1: A Survival Guide
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T1 CSU/DSUs
Figure 6-4 shows a typical CSU/DSU. It has a series of lights and a switch that is used to control the loopback test mode. The meanings of various common indicator lights are discussed in Table 6-2.
Figure 6-4. Typical CSU/DSU
Table 6-2. Common T1 CSU/DSU indicators and their meanings
|
Indicator |
Common labels |
Meaning |
|---|---|---|
|
Clear to send |
CTS, CS |
The CSU/DSU is ready to receive data. |
|
Request to send |
RTS, RS |
The DTE is ready to send data. |
|
Carrier detect |
DCD, CD |
The CSU/DSU is generating carrier signal. |
|
Send data |
TX, TXD, SD |
The CSU/DSU is transmitting pulses to the telconetwork. |
|
Receive data |
RX, RXD, RD |
The CSU/DSU is receiving pulses from the telconetwork. |
|
Loss of signal |
LOS |
When no pulses arrive within 100 to 250 bit times, LOS is declared. Under normal conditions, at least a few pulses would be present in that interval. |
|
Out of frame |
OOF |
The CSU/DSU triggers this when framing bits are in error and clears it when frame synchronization is regained. |
|
Loss of frame(red alarm) |
LOF |
The CSU/DSU asserts this when OOF has persisted continuously for 2.5 seconds. This alarm is usually cleared when frame synchronization has been obtained for at least one second, but some CO hardware may not clear the alarm for much longer (15 seconds or more). |
|
Keepalive transmission |
KA |
When framing is lost, the CSU/DSU transmits a keepalive signal to other network components.(See ... |
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