E1 and T1 interfaces

This section covers information related to E1 and T1 interfaces.

An E1 interface is logically divided into timeslots (TSs) with TS 16 being a signaling channel.

On E1 interfaces, you can create PRI groups or TS sets.

You can use an E1 interface as an ISDN PRI or CE1 interface:

• As an ISDN PRI interface, the E1 interface adopts DSS1 or QSIG signaling. As TS 0 is used to transfer synchronization information and TS16 is used as a D channel to transfer connection signaling, you can arbitrarily bind any timeslots other than TS0 and TS16 as a logical interface, which is equivalent to an ISDN PRI interface.

• As a CE1 interface with a signaling channel, the E1 interface can adopt R2 signaling, digital E&M signaling, or digital LGS signaling.

  • When R2 signaling is adopted, every 32 timeslots form a primary frame (PCM30 for example), where TS0 is used for frame synchronization, TS16 for digital line signaling, and other 30 timeslots for voice transmission. Every 16 primary frames form one multiframe. In each multiframe, TS0 in even primary frames conveys frame alignment signal (FAS) and TS0 in odd primary frames conveys non–FAS (NFAS) about link status information. NFAS provides control signaling for primary rate multiplexing. In the first primary frame, frame 0, the high-order 4 bits in TS16 convey multiframe FAS (MFAS) and the lower-order 4 bits convey non-multiframe FAS (NMFAS). TS16 in each of other 15 primary frames conveys line status information for two timeslots. For example, TS16 in frame 1 conveys the digital line signaling status of TS1 and TS17 while that in frame 2 conveys the digital line signaling status of TS2 and TS18, and so on.

  • When digital E&M signaling is adopted, the E1 interface functions as a digital E&M interface. On the interface, timeslot division and functions are the same as those with R2 signaling.

When digital LGS signaling is adopted, the E1 interface functions as a digital FXO or FXS interface. On the interface, timeslot division and functions are the same as those with R2 signaling.

After you create a TS set and configure signaling on an E1 voice interface card, the system can automatically create the voice subscriber line for the TS set.

After TSs of an E1 interface are bound to form a PRI group, the system will automatically generate the corresponding voice subscriber line.

A T1 interface can be physically divided into 24 timeslots numbered TS1 through TS24.

You can use a T1 interface as an ISDN PRI interface. The interface adopts DSS1 or QSIG signaling. Except TS24, which is used as D channel for signaling, you can arbitrarily bundle other timeslots into an interface logically equivalent to an ISDN PRI interface.

In addition to DSS1 and QSIG signaling, T1 interfaces support R2 signaling, digital E&M signaling, and LGS signaling. Configured with digital E&M signaling, a T1 interface is used as a digital E&M interface; with digital LGS signaling, a digital FXO or FXS interface.

Like E1 voice interface cards, T1 voice interface cards also have the features of voice subscriber lines.