PURPOSE: To obtain a frame switcher function and a split synthetic picture by providing a signal switching device on a camera device and connecting plural cameras in cascade.

CONSTITUTION: A signal generator 6 generates various signals synchronously with a signal outputted from a synchronous signal separator circuit 4 when the output of an external synchronizing signal detection circuit 3 is at a high level and allows the output of a crystal oscillator 5 to generate various signals when the output of the external synchronizing signal detection circuit 3 is at a low level. A CCD 7 and a signal processing circuit 8 generate a composite video signal from the output of the signal generator 6. A signal switching device 9 selects a composite video signal inputted as an external synchronizing signal or the output of the signal processing circuit 8 at a frame period set by switching period setting terminals 11a-11d. Thus, the output of a camera 1a is inputted to a camera 1b, and the output of the camera 1b is inputted to a camera 1c and then the output of the camera 1c is inputted to a camera 1d to obtain the frame switcher function without providing a special device.