The E-Sensor8 is a sensor port expansion unit that connects to securityProbe controllers or a sensorProbeX .  It is the most cost effective way to add more sensor ports to controllers. 

Additional E-Sensor8  units can be daisy chained  together and with other E-modules (E-opto16) to provide a maximum of 600 possible sensors on one controller. Up to 1000 ft (300 m)  standard CAT5 cable can be used between each device.