How They Work...

The CASE Maintenance Center employs a computer data base with complete, up-to-the-minute, near real-time alarm information on the entire call box system.

CASE’s call box system consists of five major elements:

  • A Technologically Advanced Call Box
  • The Digital Cellular Telephone Network
  • The Public Switched Telephone Network
  • The CASE Call Box Maintenance System
  • The CASE Call Box Answer Center

The call box is able to communicate with the Answer Center through radio links to cell sites. Cellular telephone networks consist of a quantity of cell sites under the control of the Mobile Telephone Switching Office (MTSO). The MTSO establishes and controls the communication path between the cellular phone (via the cell site) and the normal landline telephone system. This allows mobile customers to traverse an entire cellular system (which may include being handed off from one cell site to another), without noticeable interruption in the communication path.

Although call boxes are stationary devices, the cellular network will still command handoffs to balance the call traffic resources. Since many small cell sites are used in a system, cellular radio power output is low, allowing radios in non-adjacent cells to reuse the same frequency without interference problems. This enables a cellular system to handle many calls on a finite number of frequencies. In the event that a cell site fails, the adjacent cell sites may be able to assume additional call traffic, giving the cellular network a large degree of redundancy.

The Public Switched Telephone Network (PSTN) employs a system of telephone lines, trunks, and switching gear that routes telephone calls from the originating telephone to the destination phone number. The originating telephone provides a destination telephone number to the PSTN central office, which in turn switches the communications path to the physical location of the destination number. The telephone number specified by the call box will be passed to the PSTN by the MTSO, which will then route the call to the Answer Center. The call box can call any 7 or 10-digit telephone number using the system.

The CASE Maintenance Center employs a computer data base with complete, up-to-the-minute, near real-time alarm information on the entire call box system; thus it is able to keep the call box system virtually 100% operational. Computers running maintenance software designed for the call box are able to quickly recognize potential problems anywhere within the call box system. Abnormal situations detected by the maintenance computer are promptly displayed and printed for action by trained maintenance personnel. This assures timely repair or replacement of a problem call box. The CASE Answer Center computer utilizes a Pentium class computer, which provides all relevant call box information to the operator after decoding the ANI (Automatic Number Identification). The following information can be displayed on the Answer Center screen:

  • Call box sign number
  • Call box ANI
  • A description of call box physical location and access
  • Call box cellular telephone number
  • Area or zone information
  • Call boxes waiting for callback, with elapsed time
  • Map location
  • Time of call
  • Date of call
  • Real-time box alarm calls

The answer position computer printer records the date and time of all events from the call box system. This system will serve up to five incoming telephone lines, additional terminal positions can be added as is necessary. A single answer position can receive calls from any size system, depending on the system usage.