Any device that automatically sets a boundary value or values upon a signal. The term is usually applied to a device which, for inputs below a specified instantaneous value, gives an output proportional to the input, but for inputs above that value gives a constant peak output. A base limiter is one whose output comprises that part of an input signal exceeding a predetermined value. A slicer is a limiter having two boundary values, the portion of the signal between these values being passed on. A limiter designed to give a constant current whatever the applied voltage is a current limiter.