The Advanced Automatic Route Selection (ARS) option provides the following features:
Advanced tone detection allows the system to interpret tones received from the distant exchange or system and to act on them automatically without user intervention.
The Advanced Tone Detector is active at the following stages of a call:
After trunk seizure and before outpulsing;
After the first stage of outpulsing is complete and a second dial tone is expected;
After outpulsing is known to be complete and before answer by the called party.
An Advanced Tone Detector is connected to the audio side of the trunk after trunk seizure. Its function is to detect the arrival of dial tone from the exchange within a programmable time. The system starts to outpulse digits when either dial tone is received or the time expires. This ensures outpulsing even in situations where the tones are too badly attenuated to be recognised by the system. Alternatively, the system can be programmed to drop the trunk and give Number Unobtainable tone when the time expires.
The Advanced Tone Detector remains connected during the second stage in order to detect second dial tone (if any) so that the remaining digits of the number can be outpulsed. In some situations, for example, when connecting to a Mercury link, the second dial tone is not detected and the remaining digits are outpulsed after a delay defined on the ARS Call Progress Tone Detection form.
During the third stage, the Advanced Tone Detector remains connected for a maximum of 99 seconds after outpulsing is complete and is instructed to detect up to six call progress tones which are defined within the ARS Call Progress Tone Detection Plan.
The Advanced Tone Detector is not connected for the entire duration of the call; therefore "mid-call" tones are not detected.
Alternative routing is the automatic selection of an alternative trunk route when the first choice is busy. Routes are pre-programmed in order in the ARS Route Lists form.
Call Barring in the ARS feature allows the customer to restrict user access to trunk routes and/or specific external numbers.
Call Barring is achieved by the use of Class of Restriction (COR) values. The COR values are used to define trunk access for individual extensions or groups of extensions. All the extension users who need to access the same routes are put into the same COR groups.
The extensions in these groups are assigned the same COR value either on the Station Attributes form or the User and Device Attributes form. The CORs are then associated with trunk groups through the ARS Routes form and the Class of Restriction Groups form. This simplifies data entry by allowing identical groups of CORs to be repeatedly called into the ARS Routes form using a 1 or 2-digit index.
The Class of Restriction Groups form has a limit of 64 groups. Each group consists of a number of Classes of Restriction. All Classes of Restriction in a COR group, and hence the extensions which have been allocated these Classes of Restriction, have the same level of call barring applied to them.
Each group of extensions is associated with a trunk group via the ARS Routes form. Call Barring can be programmed to provide early call barring, where extensions whose COR appears in that group will receive Number Unobtainable tone after dialing the leading digits. This level of Call Barring is optional.
The following examples show some of the uses of Call Barring:
CORs are assigned to extensions during installation, according to customer requirements and they can be modified at any time from an Operator Console by anyone with appropriate authority.
System Speed Call entries are exempt from call barring when "YES" is entered in the "Override Toll Control" field of the System Speed Calls form.
An extension user dials an international number.
Data entry shows that the call must be completed by dialing over a local Exchange Line in Trunk Group Number 1, so Route 1 is selected.
The system finds the extension's COR from the Station Attributes form to be COR1.
Route 1 has COR Group 1 applied in data entry.
The system searches the COR Group 1 in the Class of Restriction Groups form for the extension's COR which is COR1. COR1 is not in the group, so the system ALLOWS the call to proceed.
An extension user dials an unauthorized number.
Data entry shows that the call must be completed via Private Circuit from Trunk Group 1, so Route 2 is selected.
The system determines the extension's COR from the Station Attributes form to be COR5.
The system determines the COR group programmed against Route 2 to be COR Group 3.
The system searches the COR group 3 in the Class of Restriction Groups form for the extension's COR (COR5). The presence of COR5 programmed for that group causes the system to DISALLOW the call. The extension user hears Number Unobtainable tone and users of display telephones receive the message "ACCESS DENIED".
An extension user tries to make an unauthorized external call.
The system determines the extension's COR from the Station Attributes form to be COR6.
The system determines the COR Group Number associated with the leading digit to be 64. This information is given in the header of the Automatic Route Selection form.
The system searches COR Group Number 64 for the user's COR (COR6). The presence of COR6 in group 64 causes the system to DISALLOW the call. The extension user hears Number Unobtainable tone and users of display telephones receive the message "ACCESS DENIED" after the first digit is dialed.
Expensive Route Warning Tone is a programmable option where the user hears a tone (during call setup) if the trunk group selected by the ARS is not the first in the Route List. The user then has the option of whether or not to continue with the call.
Least cost routing allows the customer to control costs by defining the order in which trunk groups are selected. This is done in the Route Plan and Route List forms. A number of different route lists can be defined to take advantage of different tariffs for different times of the day, and different days of the week. Route lists are associated with day/time zones through the programming of the Day/Time Zone and Route Plan forms.
Overlap outpulsing allows the system to seize a trunk and start outpulsing before all the dialed digits have been received. This reduces the post-dialing delay which would otherwise be caused by digit collection, trunk seizure and digit outpulsing.
The post-dialing delay (the time lapse between completion of extension dialing and the receipt of a call progress tone such as ringback) which would be experienced when using a DTMF trunk is a few seconds for a 10-digit number. Without the use of overlap outpulsing, the delay for a 10-digit number outpulsed over a dial pulse trunk would be about 16 seconds at 10 pps.
Overlap outpulsing allows outpulsing to start as soon as sufficient digits have been received to identify the route. The number of digits collected prior to outpulsing for each route listed in the ARS Routes form is defined by the customer during data entry. These digits may be subject to digit modification, prior to being passed to the appropriate sender (dial pulse or DTMF) for outpulsing. Subsequent digits are collected by the system and are outpulsed. At the end of dialing, indicated by an inter-digit time-out or the dialing of a complete digit string of known length, the sender is disconnected. The end of dialing can also be indicated by the presence of the end-of-dial character (# if programmed).
Trunk routes are seized only after the ARS process has checked the validity of the call against the caller's existing call barring instructions. In this way, false traffic is not generated at the exchange (or distant system) by aborted seizures.
This ARS feature, through the function of the Advanced Tone Detector, eliminates the need for the user to receive exchange dial tone. Secondary dial tone is a programmable option which allows the system to simulate exchange dial tone if required.
Automatic Callback allows are user who hears busy tone (all trunks in a group busy) after dialing an ARS digit string, to dial a callback access code and be queued for the first free trunk. When a trunk becomes free, the originating extension is rung back and, when answered, a trunk is seized and the previously entered digits are outpulsed.
Camp-on allows the user who hears a busy tone (all trunks in a group busy), after dialing a trunk number, to dial a Camp-on access code and remain off-hook until a trunk becomes free, or remain off-hook for a programmable period and be automatically Camped-on to the busy trunk group. When a trunk becomes free, the system seizes it and the previously entered digits are outpulsed.
