ADTRAN L128T user manual Isdn Connection

Chapter 1: Understanding ISDN and the Express L128/L128T

ISDN Connection

From the network, ISDN is delivered by a single 2-wire 2B1Q U-interface which is connected directly to the Express L128/L128T. ISDN network termi- nation is designed into the Express L128/L128T, eliminating the need and ex- pense of a separate NT1. For network testing, the Express L128/L128T responds to NT1 test commands from the telephone company central office (CO).

The Express L128/L128T has one RJ-45 jack, labeled ISDN, on the rear panel for network connection (see Figure 1-7). ISDN basic rate service divides a stan- dard telephone line into three digital channels capable of simultaneous voice and data transmission. The three channels are comprised of two bearer (B) channels at 64 kbps and one data (D) channel at 16 kbps, known as 2B+D.

The Express L128/L128T also supports a leased digital connection allowing data to be transferred at up to 144 kbps over a 2-wire facility using the same RJ-45 jack. This type of service is a permanent connection between endpoints and is sometimes referred to as a leased connection, a dedicated connection, a nailed-up connection, or a private circuit. Leased connection or leased line is used in this manual to represent these types of services.

1

POWER O

TO	TO
HUB	NIC	OFF
		ON
10 BASE T		EIA232

1	2	3	4
			ISDN

1202070L1

1

POWER O

TO	TO
HUB	NIC	OFF
		ON
10 BASE T		EIA232

1 2 3 4

2 1 ISDN

1202070L2

Figure 1-7

Express L128/L128T Rear Panel

18 Express L128/L128T User Manual 61202.070L1-1