Abstract: A novel apparatus and method of detecting loss of signal events in RF cable. The loss of signal may be caused malicious cable cuts, inadvertent disconnects, loss of signal from the cable head-end or for any other reason. The invention is particular applicable to use in cable modems which provide cable service, Internet service and telephone service to subscriber premises including both homes and businesses. All RF channels are scanned and the signal power of each is measured and compared to a threshold. If the signal power on all channels is below the threshold, then it is concluded that a “cable signal loss” event has occurred. The telephone line originating in the cable modem is shut down which causes the alarm system connected thereto to generate an alert.