Centrex Frequently Asked Questions

Get help with questions about Centrex business phone systems.

Centrex business phone systems from TELUS are built to handle the voice communication needs of any size of business.

What Does “Centrex” Mean?

The word “Centrex” is derived from "Central Office Exchange". Launched in about 1984, it became the first truly hosted and managed service and competed with Key and PBX systems. It is known today as a voice communication “one-stop shopping” solution as it provides customers with their Public Switched Telephone Network (PSTN) access, Local Access, and a vast array of features including Call Display, Voice Mail, Automatic Call Distribution (ACD), Call Forwarding, Call Transfer, Music On Hold, Conferencing, Hunting, and many more.

It also includes features that enable connectivity with other network services such as tie trunks, which connect extensions on a system to each other.

How do I customize my Centrex Voice Mail Service?

Download this guide to customizing your Centrex Voice Mail Service.

What’s going on in the background with Centrex Service?

Centrex Service is a combination of a local loop from a TELUS Central Office to a customer location, and switching hardware and software that enables voice calls to be received or initiated by a telephone set connected to the local loop.

Both internal calling between your own telephone sets and external calling (incoming and outgoing calls from the PSTN or your private network) are supported.

Normally, each Centrex line will terminate on a telephone set, unlike a Key/PBX solution.

How does my Centrex system manage calls?

Centrex Service has hundreds of features to facilitate effective and efficient management of inbound and outbound calls. Note that Centrex Services do NOT include the wiring or telephone sets at the customer premises. TELUS can, however, be engaged to provide the wiring and telephone sets at an additional charge.

The following items form the backbone of a typical Centrex phone system. You don’t have to worry about setting any of these up; this is just to demonstrate what is going on in the background with your system.

PSTN Connection

Each Centrex line is provided with one inbound and outbound PSTN connection as part of the Centrex line rate. To reach a station on the PSTN, a PSTN-access code (e.g. a "9") must be dialed before the 7- or 11-digit telephone number.

Central Office (CO) Switching Equipment

The CO Switching Equipment provides the intelligence behind the service. It supports the hundreds of Centrex features available, and directs the voice calls based on the number that was dialed.

Line Card

To connect the switching equipment to the local loops, a line card is required. Generally, two types of cards exist; an "A" card for connection to a single line set, and a "C" card for connection to a Business Set. These line cards may be located at a Remote as in the diagram above, or if a Remote is not needed to extend service to the customer location, the cards will be located in the host CO Switch.

Local Loop
Normal Centrex Service requires one loop for each telephone set. If a Meridian Business Set (MBS) is being installed, an unloaded cable pair is required, and loop length becomes a consideration.

Service Demarcation Point

The local loop will terminate at the demarcation point (first point of entry into the building) on your premises. Connection from the demarcation point to the telephone set requires you to provide, or have access to, inside wire that terminates on the telephone set jack.

What features are available on my Centrex system?

There are many features available with your Centrex system. Many are included with the system, and additional functionality is available at an extra charge.

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