10 Wiring the systemWiring the X-BUS interface74Vanderbilt Installation & Configuration Manual A6V1027695901.05.2016detectors are monitored. This is achieved by connecting 1A, 1B on the controller to2A, 2B on the first keypad or expander. The wiring continues with connection 1A,1B to 2A, 2B on the next expander and so on to the last keypad or expander. Thelast connection is 1A, 1B of the last expander to 2A, 2B of the controller. See wiringconfiguration in the figure below.1 Controller2-4 Expanders10.1.2 Spur configurationNOTICESPC52xx/53xx/63xx supports 2 spurs (2 X-BUS ports).SPC42xx/43xx supports 1 spur (1 X-BUS port).NOTICEAll expanders/keypads are fitted with a termination jumper by default. In spurconfiguration it is imperative to have these jumpers fitted.The spur (or open loop) cabling method offers a high level of fault tolerance andmay be more convenient on certain installations. In the case of a X-BUS fault orbreak, all expanders and detectors up to the fault continue to be supervised.In this configuration, the SPC controller uses a single the X-BUS port (1A/1B or2A/2B) to support a group of expanders. See wiring configuration in the figurebelow. The last expander in an open loop configuration is not wired back to thecontroller and can be identified by the fast LED flashing light (one flash every 0.2seconds approx) when in Full Engineer programming.In automatic mode, the expander numbering commences at the expander nearestto the controller and ends with the expander connected farthest from the controller.E.g. if 6 expanders are connected in an open loop configuration, then the nearestexpander on the X-BUS connection is expander 1, the second nearest expander is2, etc. ending with the expander wired farthest from the controller, which isexpander 6.
