Figures 1 and 2.) Every circuit slot in the system can be used for trunk cards or voice/data station cards. All these attributes allow the client to add future capability without breakage and re-engineering of existing equipment. Thus, the client is able to minimize initial investment while not restricting future growth.
Over time, the type of tools and facilities that a business utilizes changes. It is important that a PBX provide support for the full set of Telco network options over its installed life, even when only a subset is initially used. Trunks link two switching systems, such as System 25 and the local Central Office or System 25 and another PBX. System 25 supports five different telephone company trunk interfaces to provide desired connectivity at minimum expense. Thus the opportunity exists to select the best trunk types, depending on tariffs and customer needs.
●Loop Start (LS) trunks for public network access at minimum tariff. These trunks handle outgoing and incoming attendant calls, incoming DGC calls, outgoing pooled
facility calls, and personal line calls.
● Ground | Start | (GS) trunks for | public network | access. These trunks handle the | same | ||
type | of | calls | as | LS trunks. They provide protection against call reorigination without | |||
toll | restriction, | more reliable | automatic route | selection, virtual facilities, SMDR | and |
CAS. Simultaneous incoming and outgoing call seizure of the same trunk under heavy traffic conditions is essentially eliminated with ground start trunks. GS t r u n k s s h o u l d u s u a l l y b e s e l e c t e d i n p r e f e r e n c e t o L S t r u n k s u n l e s s t a r i f f considerations are overriding. Note, however, that Centrex Service requires LS trunks.
●Direct Incoming Dial (DID) trunks for dialing a station directly from outside
(attendant assistance not required). Outside dial access to stations, trunks (optional), and answering groups (Direct Group calling) is provided.
● Tie Trunks | for linking PBXs | with dedicated private circuits for high volume calling. |
Dial access to stations, other | trunks, answering groups (Direct Group Calling) and an | |
Electronic | Tandem Network | endpoint capability are provided. |
●Off-Premises Stations (OPS) allow a single-line voice terminal to be located remotely and connected to System 25 via arrangements with the local Telco. This service is used to provide users at secondary sites (or their residences) many of the same features as an on-premises single-line station.
To enhance the usage and control of the above set of network facilities, System 25 provides the rich set of access features outlined in the Outgoing Business Communications Section. In addition, System 25 can support networking between systems by:
. Serving as | an endpoint on an electronic tandem network (ETN) | using | its | tie trunks |
and flexible | dialing plan. |
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. Serving as an | ||||
between | usage | of | tie trunks | |
to reach a distant System 25 and then connect through that System 25 to local Telco | ||||
facilities to complete the call. |
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To support efficient | utilization of trunks, they can be grouped together | (up to | 16 | groups) if |