What is the nature of Voltage Transducer output?

Hii,
I am working on a project to Measure Voltage Amplitude using DSP development board. On DSP development board manually written "Decoding voltage amplitude derived from duty cycle encoded Voltage Sensors". So i want to know the nature of output on voltage transducer. The DSP board can only capture the pulse type signal, then calculate the duty cycle of it & from that we derived voltage amplitude.

read PWM input requirements for sensor input.
There may be a wide range of V and f inputs.
Each sensor may also have specs.