Centrex Service


Category: Telecom

Centrex is a central office-based telecommunications system owned by an outside service provider. It typically provides an agency direct dial numbers per user and does not require on-site common control equipment such as an Electronic Key System (EKS) or Public Branch Exchange (PBX). Centrex allows for easy unification of multiple sites in a centralized area by providing a common abbreviated dialing plan that can be used to dial between any two telephones that are in Centrex. Centrex provides a basic feature set and is usually delivered via analog access lines with digital lines available for larger sites. It also includes access to local and long distance calling as well as voice messaging.
Centrex system allows incoming calls to be dialed direct without the assistance of an operator. Centrex equipment is located at the local telephone company's central office premises and every telephone served by the Centrex system is directly connected to the telephone company switching center. A Centrex system offers many different features for telephone users.
The telecommunications services of the Department of Innovation and Technology (DoIT) are available to all State of Illinois agencies, boards, commissions, universities, Offices of the Illinois House and Senate, and Constitutional Officers.

Product Features and Descriptions


  • Primary Springfield (Area code 217/Prefixes 524, 557, 558, 782, 785 and 786) and Chicago (Area code 312/Prefixes 338, 793 and 814) central offices.
  • Call forwarding (inside)
  • Consultation hold
  • Call transfer
  • Three way calling
  • Call parking
  • Last number redial
  • Speed calling (individual)
  • Conference call (6 parties)
  • Automatic call back


  • Call forwarding/no answer
  • Call forwarding/busy
  • Call pickup
  • Call routing up to 5 lines 
  • Group speed calling for up to 30-70 lines
  • No outgoing call restriction
  • No incoming call restriction
  • Directed call pickup (no barge-in)
  • Directed call pickup (barge-in)
  • Ring down
  • Call forwarding (outside)

Rates and Billing

 Centrex - AT&T

Item Unit of Measure  Rate
Analog/Digital Line ​ ​$ 60.50
​Phantom Line ​$ 5.25
Carrier Charges Per Minute 110% Vendor Rates
​Toll Billing
​  Local​Per Minute​$0.02
​  Long Distance​Per Minute​$0.06
Analog Line Per Line $ 14.00
Digital Line Per Line $ 16.00
Phantom Line​ ​Per Line ​$ 0.25


Item Unit of Measure  Rate
Install Per Line
$ 13.20
Line Charge $ 22.00

Ordering and Provisioning

​Service can be procured, modified or cancelled by selecting the "Order Services" button near the top of the right pane.

DoIT Responsibilities

  • Service provisioning and implementation
  • Incident resolution
  • Routine maintenance
  • Provide support with installation estimates and planning
  • Coordinate installation
  • Provide price quotations and low-cost alternatives, clarifying order information, monitoring order status, and updating billing information. They also help with the analysis and development of the appropriate product and service mix to fulfill specific short and long term customer needs
  • Integrated ordering, inventory, and billing in a shared database that's accessible to customer Telecom Coordinators to enable service order tracking, usage reporting and billing review. Customer Telecom Coordinators also receive automatic Service Bulletins announcing changes in equipment offerings, price, and procurement procedures.
  • Provide automated agency billing - included in monthly call detail provided by DoIT Business Services
  • Coordinate training in the efficient use of products and services
  • Notify of manufacturer discontinued equipment

Agency Responsibilities

  • Develop and implement agency governance to ensure staff compliance with DoIT incident reporting and request requirements
  • Routine review of billing for errors and underutilized service and equipment
  • Consult agency's assigned Communications System Specialist (CSS) for suggested low-cost alternatives
  • Routine review of added special features
  • Provide a designated agency contact and related contact information for DoIT to interface with when needed  

Service Levels and Metrics

Service Fulfillment/Provisioning
Staff will respond to service requests during the published business hours. DoIT targets to provision this service as follows:
  • 25 lines or less within 30 business days
Incident Response and Resolution
All incidents reported to DoIT will be captured in the DoIT service management ticketing system and addressed according to the Incident Management Guidelines.
To report an incident, click here Report Problems Form or contact the DoIT Service Desk at 217-524-3648 (Springfield) or 312-814-3648 (Chicago). 
Service Availability
This service will be available 24/7 excluding planned outages, maintenance windows and unavoidable events.