Stratos HSSD-2 • INSTALLER'S HANDBOOK

8.2 Connecting a detector network to a command module120 ohm screened twisted pair such as Belden 9841 24 AWG should be used for allloop connections. The RS485 A and B wires should be taken through a ferrite (supplied)with a single loop illustrated for the power wires in section 5.3.3. The total length ofinterconnecting cable between adjacent Stratos-HSSD 2 detectors in the loop shouldnot exceed 1.2 kilometres.The detectors are connected using the RS485 connections on the terminal block(see sections 5.3.1/5.3.2) RS485 1A and 1B are the signal connections for bus 1 andRS485 2A and 2B are the signal connections for bus 2. SCREEN 1 and 2 are the screenconnections for buses 1 and 2 respectively.For the Command Module, the RS485 1A and 1B connections may be thought of as the‘Send’ lines, and 2A and 2B the ’Return’ lines. For each detector on the loop, the 1A and1B connections may be thought of as the lines from the previous detector on the loopand the 2A and 2B connections the lines to the next detector in the loop.8.2.1 Fault tolerant detector loop configurationRS485 1ARS485 1ARS485 1ARS485 1ARS485 1BRS485 1BRS485 1BRS485 1BSCRNSCREEN 1SCREEN 1SCREEN 1RS485 2ARS485 2ARS485 2ARS485 2ARS485 2BRS485 2BRS485 2BRS485 2BSCRNSCREEN 2SCREEN 2SCREEN 2CommandModuleDetector 1Detector 2 Detector 127It should be pointed out that loop connections such as above are only needed for a fullyfault-tolerant network where full isolation is required between detectors. If all detectorsare operating within the same zone a series connection can be used where the outputfrom the Command Module is taken from the Bus 2 terminals and the last detector inthe loop does not require to be connected back to the command module as shownbelow. In this example, the Command Module will not be able to monitor the networkfor communications problems but less wiring is required.8.2.2 Non-fault tolerant serial configurationRS485 1ARS485 1ARS485 1ARS485 1ARS485 1BRS485 1BRS485 1BRS485 1BSCRNSCREEN 1SCREEN 1SCREEN 1RS485 2ARS485 2ARS485 2ARS485 2ARS485 2BRS485 2BRS485 2BRS485 2BSCRNSCREEN 2SCREEN 2SCREEN 2CommandModuleDetector 1Detector 2 Detector 127Page 41Stratos HSSD-2 • INSTALLER’S HANDBOOK • Iss. 10© AirSense Technology. 2009