A transducer for producing a pulse duration modulated signal in accord with the value of a parameter. A reference capacitor-resistance circuit is provided having a predetermined rate of capacitor discharge and a second capacitor-resistance circuit is provided having a capacitor and a resistor, one of which is varied in accordance with the parameter to define a rate of capacitor discharge determined by the parameter. Each of the capacitors is periodically charged in unison to a predetermined voltage. Respective level detectors monitor the capacitor voltage charges and generate respective digital signals when the voltage charge monitored is greater than a predetermined reference below which each capacitor discharges during the time interval between charges. A logic circuit monitors the digital signals and produces a series of pulses having durations determined by the value of the parameter.