A technician has installed a door camera and modulator in a residential installation. The technician is combining the camera channel output with the analog cable TV signal using a residential distribution/combiner amplifier. At the home the technician discovers that the camera channel picture is distorted and when the camera modulator is attached, the cable TV channels show interference. The FIRST troubleshooting step should be to:

A.
call the cable company in to check that the cable signals are within the range of zero to plus two dB at the television set.

B.
replace the camera.

C.
check the signal level from the camera modulator.

D.
check cable termination of the cable TV demarcation.