# Trunk Circuit Descriptor - Digital CO

## Purpose

The Digital CO Trunk Circuit Descriptor form is used to assign signaling and timing parameters to groups of DS1 CO trunk circuits using channel associated signaling (CAS).

Use this form when performing the following tasks:

- Program T1/D4 Trunks

NOTE: The operating characteristics for all trunks are defined by the respective trunk circuit descriptor form. There are 32 trunk circuit descriptor numbers available. These must be shared between all trunks in the system. As well, each circuit descriptor number assigned must be unique. MITEL recommends that the circuit descriptor numbers be allocated to each type of trunk in blocks. For example, CO trunks may be allocated circuit descriptor numbered 1 through 4, E&M trunks numbered 5 through 12, DS1 DID trunks numbered 13 through 21, and so on.

## Field Descriptions

Parameter | Description | Default Value
Number | Enter a number from 1 to 32 to uniquely identify each entry. | Blank
Line Start Type | Select the appropriate start type for the line. | Ground
Guard Timer | Enter the amount of time for which a trunk is unavailable for seizure following a release, in increments of 50 ms. This time is required to allow the trunk to clear before re-seizing. For Loop Start trunks, a value from 800 to 1600 should be chosen. For Ground Start trunks, a value from 100 to 200 should be used. NOTE: Ground Start trunks are supported by SX-2000 Peripheral Cabinets only. | 100 ms
Ignore Far End Disconnect | Select "Yes" or "No" to indicate if ground start trunks are to ignore or respond to a far-end disconnect signal. NOTE: Ground Start trunks are supported by SX-2000 Peripheral Cabinets only. | No
Disconnect Timer | Enter the minimum length of a far-end disconnect signal. Allowed values are from 100 ms to 4000 ms in 50 ms increments. This timer must be longer than the Flash Timer. | 500
Ringing Expected | Select "Yes" to indicate that ringing is necessary for an incoming seizure to be valid. Applies to DS1 CO trunks only. | Yes
Seize Timer | Enter how long the system will wait for a "seize acknowledge" before initiating a maintenance alarm. Allowed values are from 1 to 480 units (50 ms - 24 sec), each unit being equal to 50 ms. | (200 UNITS) 10 s
Address Signalling | Select "DTMF" or "Loop" to indicate whether the trunks use loop signaling or DTMF signaling. NOTE: When systems are connected via T1/D4, the address signaling must match on either end of the connection. If one end is programmed as Loop and the other as DTMF, the dialed digits will not be translated by the receiving system, and the call will fail. | DTMF
Fake Answer Supervision After Outpulsing | Used to complete the audio connection after outpulsing if the trunk does not provide answer supervision. Select "Yes" to cause the system to provide answer supervision immediately after outpulsing. Select "No" to cause the system to wait for answer supervision from the far-end. | Yes
Release Supervision Expected | Select "Yes" to indicate that release supervision is provided from the far-end. | Yes
Ignore Answer Supervision | Specifies whether the trunk circuits are to expect answer supervision from the far-end. Select "Yes" to indicate that answer supervision is not expected. Select "No" to indicate that answer supervision is to be provided from the far-end. | Yes
Audio Inhibit Until Answer Supervision | Used to prevent a DTMF receiver, in line split mode, from being connected between the originating party and the outgoing trunk during the digit outpulsing phase of the call processing cycle. Select "Yes" to indicate that the audio path will only be connected after answer supervision has taken place. | Yes
Far End Connection | Not applicable to this release. | Local Office
Drop Digit Rcvr for Outgoing Audio Before Ans Sup | This option allows DTMF digits to be sent from a telephone to the CO without having to wait for or fake answer supervision. It also allows the system to provide exact call detail through SMDR by using the answer supervision signals provided by the CO. Select "Yes" for credit or calling card calls, calls that require pin numbers, and equal access calls. For example, if the CO recognizes a calling card call, it will send either a tone or recorded message. Once the user enters a valid card number, the call proceeds and answer supervision is returned when the called party answers. | No
Flash Timer | Enter a value between "200" and "700" milliseconds in increments of 50 milliseconds. This timer specifies the duration of the single trunk flash or each of the flashes for a double trunk flash. For a double flash, the time between flashes is hard-coded at one second. | 300 ms