ADTRAN specifications Figure A-1. FT1 Loopbacks

APPENDIX A

FT1 LOOPBACKS

1. GENERAL

This Appendix is an overall reference to the loopback capabilities of the ADTRAN Fractional T1 system. Included in the Appendix is a description of the FT1 loopbacks and the methods for activating the FT1 loopbacks.

2. FT1 LOOPBACKS

Figure A-1 shows the application from the central office (CO) to customer premises. The FT1 Repeater is shown for convenience and not as a necessary part of the FT1 network. The loopbacks shown are as follows:

A.FT1 DP network loopback

B.FT1 DP CPE loopback

C.FT1 Repeater network loopback

D.FNID network loopback

E.FNID CPE loopback

There are two loopbacks available to the FT1 DP. The FT1 DP network loopback loops the FT1 signal back to the network. The FT1 DP CPE loopback loops the FT1 signal back to the customer.

The FT1 DP network loopback is a digital loopback toward the CO (see Figure A-2). This loopback is initiated by the OCU latching loopback command (N1010101), by a push-button when available, or by the craft interface. The OCU latching loopback code is detected in the primary DS0 of the FT1 circuit -- the channel where the FT1 DP is physically installed -- to control the FT1 circuit looping. When the FT1 circuit is looped, all DS0s in use will be looped back toward the network. The DS0s will be transmitted on to the customer.

The FT1 DP CPE loopback is a digital loopback toward customer premises as shown in Figure A-3. This loopback is initiated by the RLB button on the FNID, or by the craft interface. When the FT1 circuit is looped, all DS0s in use will be looped back toward the customer. All DS0s sent toward the network will be filled with all-1s.

DSX-1				FT1
Interface	FT1 DP				FNID	T1 NIU	Customer
				Repeater
							Premises
Central							Equipment
	A	B	C		D	E
Office
	D4
	Channel Bank
				Figure A-1. FT1 Loopbacks

DSX-1 Interface

Central Office

FT1 DP

D4

Channel Bank

HDSL

Local Loop

FNID

DS1 Interface

Customer Premises

Figure A-2. FT1 DP Network Loopback

DSX-1 Interface

Central

Office

FT1 DP

D4

Channel Bank

HDSL

Local Loop

FNID

DS1 Interface

Customer Premises

Figure A-3. FT1 DP CPE Loopback

61245211L1-5A Section 61245211L1-5, Issue 1 A-1