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Case Study

The Oxfordshire Fire and Rescue Service contacted Sentry Telemetry enquiring about using GSM as a tertiary alarm system. Accordingly, our SentryGSM3Alarm device was used as the basis to develop an application specific solution.

Pre-defined SMS text messages are sent to the duty fire fighter’s mobile phones, in response to push button inputs (or PC remote triggered) to suit the alarm condition. After a series of trials and refinement with the Fire Service, the bespoke solution is being rolled out as the county wide standard.

Project Objectives

The Fire Service specified various key parameters that were core to providing an easy to use, reliable alarm system:

  • 4 inputs and 4 outputs
  • Alarms sent via SMS using dual band, standard SIM cards
  • Progammable and controllable remotely via SMS
  • 12-14Vdc operation
Possible Alarm Actions
  • Relay(s) ON permanently or ON for ‘x’ seconds, then OFF
  • Relay(s) OFF permanently or OFF for ‘x’ seconds, then ON
  • Send Alarm notifications via SMS to a list of recipients
  • Relay incoming pager message to a list of recipients by SMS



The SentryGSM3Alarm is a quad band device using a standard GSM SIM card. The multifunction controller is designed to accept up to four digital (volt free) inputs and has four relay outputs. For each input triggered, up to five combine actions may be programmed.

User Defined Parameters

(These include, but are not limited to):

  • Normal state of input 1,2, 3 and 4
  • Actions taken when inputs 1,2, 3 or 4 are triggered
  • Alarm messages for input 1, 2, 3 and 4
  • Recipients for messages 1, 2, 3 and 4
  • Recipients for pager relay
  • 3 messages per input
  • 20 recipients per message


Remote Sensing, Monitoring & Metering

Oxfordshire Fire & Rescue Service
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