# Trunk Circuit Descriptor - CO

## Purpose

The CO Trunk Circuit Descriptors form is used to assign signaling and timing parameters to groups of CO trunk circuits (loop start). This form completes the basic definition of CO trunk characteristics.

NOTE: Ground start trunks are no longer supported by the MiVoice Business system.

Use this form when performing the following tasks:

- Program a ASU

- Program a 3300 Universal ASU

- Program Analog Trunks

- Program Embedded Analog

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 the unique number that is used to reference the CO trunk characteristics in the Analog Trunks form. | Blank
Line Start Type | Select "Loop" if the trunks assigned to the circuit descriptor are loop start. Ground Start trunks are no longer supported by the MiVoice Business system. | Loop
Post Call Metering | Select "Yes" to count meter pulses during and after a call. Select "No" to only count meter pulses during a call. | No
Guard Timer | Enter a value that specifies the amount of time for which a trunk is unavailable for seizure following a release (in increments of "50" milliseconds). The time is required to allow the trunk to clear before reseizing. For Loop Start trunks with no Post Call Metering, enter a value from "800" to "1600". For trunks employing Post Call Metering, enter a value from "3000" to "8000". NOTE: Ground Start trunks are no longer supported by the MiVoice Business system. | 100 ms
Calling Party Disconnect | Select "Yes" if the disconnect signal on incoming trunk calls is to be provided by the far-end connection. This is used when the CO is a "calling party hold" type. The trunk cannot be used until the far end clears down. Select "No" to indicate that the trunk can be cleared down by the system. | No
Dictation Trunk | Select "Yes" if the trunks have access to remote dictation services. Select "No" to indicate that dictation services are not available. | No
Ignore Far End Disconnect | Select "Yes" if the trunk circuits are to ignore a disconnect signal from the far-end. Select "No" and the trunk circuit will respond to a disconnect signal from the far-end. | No
Disconnect Timer | Enter the duration of the disconnect signal timer. Allowed values are from "100" to "4000" milliseconds, in 50 millisecond increments. This value defines the minimum acceptable duration of a disconnect signal from the far-end. This timer must be longer than the Flash Timer. | 500 ms
Ignore Far End Reversal During Seizure | Select "Yes" if reversal signals are to be ignored. Select "No" to cause a reversal from the far-end to be recognized as a seizure signal. | Yes
Ringing Expected | Select "Yes" if ringing is necessary for an incoming seizure to be valid. When this option is set to "Yes" and the Ignore Far-End Reversal option is set to "No", a reversal from the far-end will prevent the trunk from being seized for outgoing calls. However, ringing has to be present for a valid incoming call. Select "No" to indicate that Ringing trunk), or a reversal (if Ignore Far-End Reversal is "no") will all be acknowledged as incoming calls. NOTE: Ground Start trunks no longer supported by the MiVoice Business system. | Enabled (yes) [UK - Disabled (no)]
Seize Timer | Enter the duration of the seize timer. Allowed values are from "10" to "1800" seconds. This timer defines how long the system will wait for a "seize acknowledge" before reporting a maintenance alarm. | 10 s
Address Signalling | Select "Loop" if the trunks use only loop signaling. Select "DTMF" if the trunks use 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 | This option is used to complete the audio connection after outpulsing if the trunk does not provide answer supervision. Select "Yes" if answer supervision is to be provided by the PBX immediately after outpulsing. Select "No" to cause the system to wait for answer supervision from the far-end, if any is provided. | Yes
Ignore Answer Supervision | Select "Yes" if the system is to ignore answer supervision from the far-end. Answer supervision is generated by using times and/or tone detectors. Select "No" to indicate that Answer Supervision from the far-end is to be accepted. | Yes
Release Supervision Expected | Select "Yes" if the trunk circuits are expecting release supervision from the far-end. Select "No" to indicate that the trunk circuits do not provide release supervision. The system will not allow two trunks designated as "No Release Supervision Expected" to be connected together. | Yes
Audio Inhibit Until Answer Supervision | This option is 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. It is used for sites that are tied to very sensitive central offices or remote PBXs. When enabled, the audio path is fully connected and the two parties will be able to talk only after the answer supervision has taken place. Select "Yes" if a DTMF receiver, in linesplit mode, is NOT to be connected between the originating party and the outgoing trunk during digit outpulsing. Select "No" if a DTMF receiver, in linesplit mode, IS to be connected between the originating party and the outgoing trunk during digit outpulsing. | Yes
High Loss Option | Not applicable to this release. | No
Balance Network Setting | This field only applies to LS trunks that are supported by the ASU I. You program the Balance Network Setting for all other LS trunks in the Analog Trunks form. Balance Network Settings define the impedance at which the two to four wire hybrid circuits are balanced. The setting affects side-tone on a low delay network, and echo in an IP network. The available options are: 600 — if the load presented to the trunk port is resistive, (loaded cable, broadband system) National Complex — if the load is capacitive (long unloaded cable) Default is National Complex. NOTE: The impedance values used for each setting vary by country or region and according to whether the LS trunk is connected to an IP port. For a list of impedance values, consult the Hardware Technical Reference Manual. | National Complex
Trunk Category | This field only applies to LS trunks that are supported by the ASU I. You program this field for all other LS trunks in the Analog Trunks form. For short analog CO trunks (ACO Short) select "Short". For long analog CO trunks (ACO Long) select "Long". If you select "Unknown", ACO Short is applied. Default is Short. NOTE: For Loop Start trunks, the Trunk Category setting is applied on a per trunk basis. For non-Loop Start trunks this setting is applied based on the Trunk Circuit Descriptor. If you change the Trunk Category setting for a non-Loop Start trunk, the setting is applied to all trunks that share the same Trunk Circuit Descriptor number. | Short
Perform seize test on out-of-service trunks | This option is used to ensure that a trunk is working correctly before being returned to service. When maintenance places a circuit into an out-of-service state it generates a log indicating a state change from idle to out-of-service. A background diagnostic process is then initiated to perform a series of tests on the trunk, which include a seize test. After the trunk has passed the tests it is returned to service. Select "Yes" and the test is done automatically. Select "No" and the trunk will remain in an out-of-service state until the tests are run. | Yes
Ground Condition During Busy Out | Select "Permanent" to indicate the trunk is grounded when busied-out or "Removed" to indicate the trunk is removed from the circuit. | Removed
First Meter Pulse Is Answer | Select "Yes" to indicate to call processing that the first meter pulse sent by the central office also signals that the far end has already answered a call. If this option is set to "Yes", then Ignore Answer Supervision must be set to "No". | No
Minimum Ring Detection Timer | Enter a value for the duration of ringing signal expected from the CO. The valid range for this field is 200 to 500 milliseconds, in steps of 50 milliseconds. | 200 ms
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
Call Clearing Signal | Select "Reversal" to clear a call in the connected state by checking for line reversals after 500 ms from seizure. Enter Disconnect to disable the Call Clearing Signal checking. | Disconnect
AC Impedance | Not applicable to this release. NOTE: AC impedance values are determined by the setting in the Balance Network Setting field. For a list of impedance values, consult the Hardware Technical Reference Manual. | Not Applicable
CLASS Trunk | Select "Yes" if the trunks use LS CLASS (Loop Start-Custom Local Access Signaling Services). (Embedded analog trunks only.) LS CLASS allows the MiVoice Business system to pass Calling Line ID digits and CLASS name information over Loop Start trunks to display sets that support Caller ID functionality. | No
Milliwatt Tone | Enter the Central Office telephone number that provides Milliwatt tone to the trunks during testing using the Line Measure Tool. | Blank
Silence Tone | Enter the Central Office telephone number that provides Silence tone to the trunks during testing using the Line Measure Tool. | Blank