AT&T 7400 series Interdigit Time-out, Intermediate High-Usage Trunk Group, Intermachine Trunk IMT

C-10TRUNKING TERMS AND CAPABILITIES

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∙100-milliseconds——for DIMENSION PBX switches.

Interdigit Time-out

The maximum number of seconds that the switch can wait from one digit to the next digit before a time-out occurs and a retry is required. This is a switch parameter related to call origination. The DIMENSION PBX use 10 seconds as the time-out. System 75 and Generic 1 use a default time-out of 5 seconds. However, the switch may be optioned, via administration, to provide any value from 5 to 99 seconds. System 85 and Generic 2 use values within the range of 6 to 18 seconds. The specific value is dependent upon the particular trunk type.

Intermediate High-Usage Trunk Group

Generally, these trunk groups are second- or third-choice trunk routes. Typically, this category of trunk group receives route-advance overflow traffic from a High-Usage Trunk Group. Refer to ‘‘High-Usage Trunk Group.’’

Intermachine Trunk (IMT)

Another name for the ‘‘High or Intermediate High-Usage’’ tie trunk groups. Calls are routed to these trunk groups via the AAR software.

Intertandem Trunk

A term frequently used when ETN trunking facilities are described. Actually, an ‘‘Intertandem Trunk’’ is a particular application of a 4-wire tie trunk. Specifically, those tie trunks connect one ETN tandem switch node to another ETN tandem switch node.

Loop Start

A trunk supervisory signal initiated by the PBX by completing the loop current path. For outgoing- originated calls, the switch dial tone detector determines when digit sending (start dial) may begin. AT&T does not support loop start trunks.

MF (or Multi frequency)

An inband signaling method that, in terms of operation, is similar to DTMF. However, MF uses different tones. The MF method has traditionally only been used to provide interoffice communication between COs. Although not recommended, the System 85 (R2V3 and R2V4) and Generic 2 may be configured to provide MF signaling. However, a special development charge is associated with the MF option.