Modules for the PDW90 base station are easy to install and add functionality to the wireless system. There are four types of modules available: dual analog inputs, dual analog outputs, digital I/O, and dual relays. The analog outputs module allows the base station to output two independent analog signals being broadcast by any of the field units. The analog inputs module allows the base station to accept two analog signals and transmit them wirelessly to any of the connected field units. The digital I/O module contains four channels which can be programmed to correspond with any of the field units’ digital inputs or outputs. The dual relays module can also be controlled from any of the connected field units’ digital I/O.