A firearm accessory mounting apparatus comprises of a clamp body with multiple split sockets. The invention enables discrete isolation of the intricate spatial and temporal detail in morphology of the atrial activity of interest from superimposed ventricular activity of a preceding heartbeat in a particular arrhythmia. Preferably the first responders can view not only the emergency caller’s information for those E911 calls that they are responding to, but also information about other emergency callers that other first responders are responding to. A buffer may be coupled to each of the plurality of serial interface engines and an interface controller. The controller conducts control so that the corrector corrects the video signal input to the input unit according to the color of light detected by the first detector if the second detector detects that the pattern portion formed of the single color of black or white is contained in the video signal input to the input unit.