Appendix K System region attributes 237
BCM50 Installation and Maintenance Guide
Digital trunk types
Table 60 provides a description of the types of digital trunk types.
Note that some of these line types are available only when specific regions are chosen.
Table 60 Digital trunk types and descriptions (Sheet 1 of 2)
Digital trunk
types
Description
T1/E1 Digital line that carries data on 24 channels at 1.544 Mbps (North American); 30 channels
at 2,048 Mbps (Europe)
Loop, E&M, DID and ground start lines are also versions of T1 lines.
You can program auto-answer T1 loop start, T1 E&M trunks, T1 DID, T1 ground start
trunks, PRI and IP trunks to map to target lines to provide for attendant bypass (calling
directly to a department or individual) and line concentration (one trunk can map onto
several target lines).
DID This is a type of T1 trunk line that allows an outside caller to dial directly into a line on the
BCM50.
Loop This is a type of T1 line. This type of line is used on systems where the service provider
supports disconnect supervision for the digital loop start trunks.
These trunks provide remote access to the Business Communications Manager from the
public network. This trunk must have disconnect supervision to allow the trunk to be set to
auto-answer, which provides the remote access portal.
Ground T1-groundstart trunk
These lines offer the same features as loop start trunks, but are used when the local
service provider does not support disconnect supervision for digital loop start trunks.
Ground start trunks work with T1 only. By configuring lines as ground start, the system
recognizes when a call is released at the far end.
E&M T1 and E&M. This type of trunk line is used to create simple network connections to other
phone systems.
This trunk always operates in a disconnected supervised mode.
PRI ISDN interface with 23 B channels and 1 D channel at 1.544 Mbps (in Europe: 30
B-channels and 1 D-channels at 2.048 Mbps).
These lines give you incoming and outgoing access to an ISDN network and are
auto-answer trunks.
BRI ISDN loop that provides both T and S reference point loops.
These loops can support both network (T and S loops) and terminal equipment (S loop)
connections.
This type of line provides incoming and outgoing access to an ISDN network. ETSI ISDN
BRI is the European Telecommunications Standards Institute specification for BRI ISDN
service. BRI provides two bearer B-channels operating at 64 kbits/s and a data D-channel
which operates at 16 kbits/s. The D-channel is used primarily to carry call information. Like
loop start trunks, BRI lines can be configured as manual-answer or auto-answer.
DASS2 (British) Trunk provides multi-line IDA interconnection to the British Telecom network.
