Introduction

The T1 interface terminates or distributes T1 facility signals for the purpose of processing the SS7 signaling links carried by the T1 carrier. The T1 interface can be either an E1/T1 MIM or an HC-MIM, or an E5-E1T1 card as shown in Figure B-1 and Figure B-2. The E1/T1 MIM, HC-MIM, or E5-E1T1 card can also be used as an E1 interface. This appendix describes how the T1 interface is configured. The E1 interface configuration is described in E1 Interface The E1/T1 MIM contain up to eight signaling links and allows the EAGLE to contain more than 500 signaling links.

Figure B-1 E1/T1 MIM Block Diagram

Figure B-2 HC MIM or E5-E1T1 Block Diagram

Table B-1 provides an overview of the functions of the T1 card and the channel card.

Table B-1 Functional Overview of the T1 and Channel Card

Card	Function
T1	Connectivity of both T1 interfaces to a 100 Ohm interface. Processing of a total of eight time slots from the T1 interfaces Interface T1 port 1 through an external backplane to channel cards for processing of additional time slots
Channel	Processing of eight time slots from the T1 interface Interface through an external backplane to a T1 card to process eight time slots

Configured as a T1 Card

Configured as a T1 card, two separate and independent T1 inputs can be terminated on a T1/channel card. From one or two bi-directional T1 facility inputs, one to eight bi-directional channels are extracted and processed as SS7 signaling links. Implemented as T1 Link Interface Modules, up to 24 separate and independent T1 inputs can be terminated in an extension shelf. The transmission rate of signaling links on the MIM card must be 56 kbps.

Configured as a Channel Card

In an extension shelf equipped with the T1 backplane, a T1 configured card terminates one or two T1 inputs and connects the T1 port 1 input to one of eight available busses on the T1 cabling backplane. Other T1 cards configured as channel cards also connected to the T1 cabling backplane are able to extract any eight signaling channels from the same T1 port 1 input. The transmission rate of signaling links on the MIM card configured as a channel card must be 56 kbps.

Note:

An HCMIM or an E5-E1T1 card cannot be used as a channel card.

High Capacity Multi-Channel Interface Module (HC-MIM) and Eagle 5 - E1 T1 Interface (E5-E1T1)

The High Capacity Multi-Channel Interface Module (HC-MIM) and EAGLE 5 - E1 T1 Interface (E5-E1T1) provides access to eight T1 ports residing on backplane connectors A and B. Each data stream consists of 24 T1 DS0 signaling links assigned in a time-division multiplex manner. Each channel occupies a unique timeslot in the data stream and can be selected as a local signaling link on the interface card. A maximum of 64 T1 signaling links can be assigned to an HC-MIM. A maximum of 32 T1 signaling links can be assigned to an E5-E1T1 card.

To support the processing of signaling channels that are intermixed on trunks with voice or data channels, the HC-MIM and E5-E1T1 card allows T1 ports to be channel bridged. This allows better utilization of T1 bandwidth without dedicating entire trunks to signaling.

Figure B-3 Channel Bridging

Channel bridging is implemented by pairing odd and even T1 ports. The T1 port selected for channel bridging is the odd numbered port (1, 3, 5, 7). When the T1 port is selected for channel bridging, it is paired with its adjacent even numbered port (2, 4, 6, 8) as shown in Table B-2.

Table B-2 Channel Bridging T1 Port Pairing

Odd Numbered T1 Port (Bridging Master)	Even Numbered T1 Port Bridged to the Odd Numbered T1 Port (Bridging Slave)
1	2
3	4
5	6
7	8

By pairing T1 ports, the adjacent even numbered T1 port could be used to allow data received on the bridging master (odd) T1 port to reach downstream network elements. This interface is a bi-directional interface so data is also able to enter the bridging slave (even) T1 port and leave the EAGLE through the bridging master (odd) T1 port. There is a 1 to 1 correspondence between the timeslots on the bridging master and slave T1 ports.

In order to use channel bridging without facility errors, both T1 ports (bridging master and slave) must be synchronous (timed off the same clock source). This may be accomplished in one of the following ways:

• The bridging master T1 port and the bridging slave T1 port use timing recovered from each other (using the t1tsel=recovered parameter with either the ent-t1 or chg-t1 command). When provisioning channel bridged T1 port, only the bridging master T1 port is provisioned with the ent-t1 or chg-t1 command. The bridging slave T1 port is automatically provisioned with the same attributes as the bridging master T1 port.
• Both the bridging master and slave T1 ports are using an external clock source (using the t1tsel=external parameter when provisioning the channel bridged T1 port with either the ent-t1 or chg-t1 command).

Any other methods used for timing could cause problems on the T1 trunk and are not be supported.

Idle patterns on the shadow channels, that is, the timeslots located on the bridging slave T1 port that have been not been dropped from the bridging master T1 port, are provided by the EAGLE. All other idle timeslots that are not dropped by the EAGLE must contain an idle pattern provided by the remote network elements connected to both T1 ports (bridging master and slave). Without these patterns on the idle timeslots, instability of the T1 signaling link may occur.

Provisioning of signaling links on the bridging slave T1 port is not allowed while the bridging master T1 port is channel bridged.