Patton electronic 2720 Loop V.54 & Telco Diagnostics, Operating Local Loopback LL, T1/FT1 CSU/DSU

5.2 LOOP (V.54 & TELCO) DIAGNOSTICS

The NetLink-T1™ offers three V.54 loop diagnostics and is com- patible with two Telco loop diagnostics. Use these diagnostics to test the CSU/DSU and any communication links. These tests can be acti- vated 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-T1™, and is performed separately on each unit. Any data sent to the local NetLink-T1™ in this test mode will be echoed (returned) back to the user device (i.e., characters typed on the key- board of a terminal will appear on the terminal screen).

	T1/FT1 CSU/DSU	T1/FT1 CSU/DSU
	Model 2720/I	Model 2720/I
			Ethernet
		Receive
Ethernet	Internal
	Clocking	Recover	Device
Device		Clocking

Clock/		Cable Span	Clock/
Data		Data	Data
Clock/			Data
Data	Model 2720/X	Model 2720/I
		LLB Initiated

Figure 8. Local Loopback

To perform a LL test, follow these steps:

1.Activate LL. This may be done in one of two 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. Toggle the front panel switch to the “Local” position.

2.Verify that the data terminal equipment is operating properly and can be used for a test.

3.Perform a V.52 BER (bit error rate) test as described in Section 5.3. If the BER test equipment indicates no faults, but the data terminal indicates a fault, follow the manufactur- er’s checkout procedures for the data terminal. Also, check the interface cable between the terminal and the NetLink-T1.

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5.2.2 Operating Remote Digital Loopback (RL)

The Remote Digital Loopback (RL) test checks the performance of both the local and remote NetLink-T1™, as well as the communication link between them. Any characters sent to the remote NetLink-T1™ in this test mode will be returned back to the originating device (i.e, char- acters typed on the keyboard of the local terminal will appear on the local terminal screen after having been passed to the remote NetLink- T1™ and looped back).

	T1/FT1 CSU/DSU	T1/FT1 CSU/DSU
	Model 2720/I	Model 2720/I
			Ethernet
		Receive
Ethernet	Internal
	Clocking	Recover	Device
Device		Clocking

Clock/		Cable Span	Clock/
Data		Data	Data
Clock/		x	Data
Data	Model 2720/I	Model 2720/I
	RL Initiated

Figure 9. Local Loopback

There are two Remote Loops that can be initiated from the NetLink-T1 unit: (1) V.54 Loop, and; (2) CSU Loop. The user can select the type of loop that can be initiated from the System Diagnostics/Statistics screen or with Switch S1-1. When a loopback is initiated this is the type of loop that the unit uses to loop up the remote unit. NOTE: The NetLink-T1 will respond to both loops regard- less of the state of the RDL Type.

To perform an RDL test, follow these steps:

1.Activate RDL. This may be done in two ways:

a.Enter b Remote Loop from the System Diagnostics/Statistics menu and toggle the <Spacebar> until “RL” appears next to theb Remote Loop option.;

b.Set the front panel switch to ‘Remote’.

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