Abstract: An alert system for providing an alert of an actual or impending emergency to homes, businesses and the like. The alert system is used in cable system network over which communication signals are transmitted to a receiver remote from the transmitter. Such communication signals have associated therewith at least one distinguishable modulation frequency. The alert system includes a mechanism for receiving an alert request and a transmitter for transmitting an alert signal in response to the alert request. The transmitter is coupled with the cable system and generates an alert signal which is modulated at a frequency distinguishable from the frequencies of the communication signals. The transmitter includes a sideband filter to reduce the subharmonics generated around the alert signal frequency. The receiver includes a mechanism for detecting a valid alert signal from the alert signal received and for generating an alarm signal therefrom.