The Model 2220 is a Quad channel pulse meter interface with integrated Modbus communication capability. Modbus is a very popular open communication standard that is available on many third party controllers, data acquisition systems and man-machine interfaces. The Model 2220 is self-contained. It contains the Quad dry contact switch inputs, processor, power supply and an isolated RS485 communication interface. The dry contacts can be a mechanical relay, solid state relay or a pull to ground NPN type output. Up to 1K Ohm total contact and wiring resistance is tolerated. The inputs can also tolerate a voltage of up to 60 VDC.