video switch 113 couples the true output of the video switch 112 to the comparator 110 the other input of the comparator 110 is coupled to a reference source 118 to receive a reference value or signal representing a level slightly higher than normal white level from the foreground image the output of the comparator 110 is coupled through a gate 120 and through a gate 122 to the video switches 58 72 84 and 102 respectively the outputs of the video switches 58 72 84 and 102 are respectively coupled through a plurality of line drivers 130 132 134 and 136 each of the video switches 58 72 84 and 102 is coupled between a signal output and a pair of inputs carrying like color signals from the two different cameras 10 and 14 the video switches are bistable and are switched to one or the other of their states by the comparator 110 to couple either the foreground signals or the background signals to the outputs whenever the comparator 110 determines that the average intensity signal from the matrix 108 is less than the reference value from the reference source 118 the video switches 58 72 84 and 102 are caused to assume an appropriate state to pass the foreground signals to the outputs conversely when the average intensity signal exceeds the reference signal the various switches are switched to provide the background signals to the outputs the gates 120 122 amplify the signals at the output of the comparator 110 to the extent necessary to drive the various video switches 58 72 84 and 102 in addition the gates 120 and 122 provide for the display.