Do Apollo's analogue addressable detectors use digital protocol?

In 1986, Apollo Fire Detectors introduced a range of analogue addressable detectors called Series 90. The Series 90 protocol has proved extremely reliable and robust. Therefore when it came to designing protocol for XP95, the basic concept was not tampered with but added to. Timings, voltage and current specifications as well as type codes remain consistent. XP95 is compatible with Series 90 products and control equipment. The extended protocol allows for further types of devices to be connnected to the loop. The principle of compatibility has stood the test of time and the next generation of Apollo detectors, the Discovery range, uses a protocol that is entirely compatible with Series 90 and XP95. The Discovery protocol is distinguished from the Series 90 and XP95 protocol by its additional operating modes - 'read' and 'write'. For most of the time the system operates in normal mode which is almost identical to XP95.

Although Series 90, XP95 and Discovery are all analogue addressable devices, they use digital protocol for panel/device communication. Within the detector there is an electronic circuit that converts the analogue signal to a digital one. This is called the A/D converter.

Voltage pulses of between +5V and +9V above the DC pedestal level are superimposed on the supply voltage. The detectors are sensitive to either smoke or heat and produce an analogue signal which corresponds to the amount of smoke or heat present around the detector. This analogue signal is converted to digital form by the A/D converter and is transmitted to the control panel synchronous on-off current pulse response.

Apollo has a digital, open protocol.

For a fuller exploration of these issues, please download our Protocols PIN sheet PDF.