The Type A controllers require 4 to 20-mA signals from a temperature controller or slide-wire potentiometer. Input signals are optically isolated. Other features include solid-state output stages; up-down or circular operating modes; logic status lights; choice of current, voltage, or resistance input; 10-stage capacity; and fused output stages. Type B units with input cards that require no driver or temperature-controller input signal are available for boiler applications. All units are cRUus-compliant.
