status of the transmit clock.

ALM

The alarm LED indicates the presence of a

 

Blue or Yellow Alarm, or Out of Frame con-

 

dition. The ALM LED will blink on every half-

 

second. Alarms may occur due to:

 

• Loss of Synchronization

 

• Loss of Frame

 

• AIS (Blue Alarm)

 

• RAI (Yellow Alarm)

ERR

The error LED indicates various error condi-

 

tions, including framing bit errors, excessive

 

zeros, controlled slips, severe errors, or bit

 

errors (when sending V.52 test patterns).

 

When sending a test pattern, the LED will

 

remain lit if the unit does not receive the

 

identical pattern. When it receives the cor-

 

rect pattern, the LED will turn off. If error

 

insertion is on, the LED will blink once a

 

second if everything is operating properly.

TST

The test indicator LED blinks with a specific

 

pattern depending on the type of test mode.

 

When the unit is in local analog loop, the

 

LED will blink on briefly. When the unit is in

 

remote loop, the TST LED will blink off

 

briefly. When the unit is sending a test pat-

 

tern or is putting the remote unit into

 

V.54/CSU loopback, the TST LED will stay

 

on. These are the test modes:

 

• V.54/CSU Loopback & V.52 Patterns

 

• Local Loopback

PWR

The power indicator LED will remain lit while

 

the unit is powered. It turns off when the

 

unit is not powered.

5.2 LOOP (V.54 & TELCO) DIAGNOSTICS

The NetLink-E1™ offers three V.54 loop diagnostics and is compatible with two Telco loop diagnostics. Use these diagnostics to test the CSU/DSU and any communication links. These tests can be activated via the software control port (See Section 3.2.3 System Diagnostics), via signals on the serial port interface or the front panel switch.

5.2.1 Operating Local Loopback (LL)

The Local Loopback (LL) test checks the operation of the local NetLink-E1™, and is performed separately on each unit. Any data sent to the local NetLink-E1™ in this test mode will be echoed (returned) back to the user device (i.e., characters typed on the keyboard of a terminal will appear on the terminal screen).

 

 

 

 

 

 

G.703/G.704 NTU

 

 

 

 

G.703/G.704 NTU

 

 

 

 

 

 

 

 

 

 

 

Model 2701 RC

 

 

 

 

Model 2701 RC

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Serial

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Serial

 

 

 

 

Internal

 

 

 

 

Receive

 

 

 

 

 

 

 

 

Clocking

 

 

 

 

Recover

 

 

Device

 

Device

 

 

 

 

 

 

 

 

Clocking

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Cable Span

 

 

 

 

 

 

 

 

 

 

 

 

 

Clock/

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Clock/

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Data

 

 

 

 

 

 

 

 

 

 

 

 

 

Data

 

 

 

 

 

 

Data

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Clock/

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Data

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Data

 

 

 

 

 

 

 

 

 

 

 

 

 

Model 2701 RC

 

 

 

 

 

 

 

 

 

 

Model 2701RC

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

LLB Initiated

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Figure 7. Local Loopback

To perform a LL test, follow these steps:

1.Activate LL. This may be done in one of three ways:

a. Enter

 

a

Local Loop from the System

Diagnostics/Statistics menu and toggle the <Spacebar>

until

LL appears next to the

a

Local Loop option.

b.Activate the LL signal on the DTE. If you are not sure which lead is the LL signal, please refer to Appendix D.

c.Toggle the front panel switch to the Local position.

39

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