Excellent example of the discontinued Trace Elliot Quad Chorus Pedal. This is highly versatile, with 2 inputs and 2 outputs - use of just 1 input allows a stereo effect.

18v power supply unit included.

From the manual:

This unit is a versatile pedal with two completely independent high quality digital chorus effects built in. In stereo mode, the signal path is true stereo throughout, with a separate processor for each channel. This enables a different rate of chorus for the left and right outputs, for example, to create a richer sound without any periodic "cycling" typical of some cheaper units. Furthermore, in stereo mode the unit can be used with two instruments; each instrument can have it's own chorus effect and dedicated output. This facility is also useful when bi-amping a bass rig where you would want a slower chorus on thelow frequencies than on the high. In quad mode, the two chorus units are cascaded in series, with the output of chorus onefeeding into the input of chorus two. This mode provides a rich, heavily textured soundthat creates a dramatic effect, especially when run in stereo. In quad mode, only input one is used as both chorus processors are used on the same signal for greater depth of effect.