To provide a signal processor which controls the operating timing excellently at all times, is made at a low-cost and miniaturized or realizes miniaturization of a system.

The signal processor (imaging apparatus) 200 capable of making communication with a plurality of apparatuses (strobe flash units) 300(1), 300(2) through prescribed communication means (USB) 220 to 224 and executing active operations in one imaging operation through interlocking with a plurality of the apparatuses 300(1), 300(2) issues timing information (information utilizing a frame number of a start of frame packet) for operation control such as imaging via the prescribed communication means (USB) 220 to 224.