The invention pertains in general to commercial and residential fire and security alarm systems.
Such alarm systems, and in particular residential alarm systems, may use RF (radio frequency) links between alarm sensors such as magnetic door/window contacts, infrared motion detectors and the like and a main control panel. More specifically multiple RF transmitters are typically used to send messages from the alarm sensor to the main control panel. The RF signals are in accordance with Federal Communications Commission (FCC) rules and regulations transmitted at approximately 315 mHz.
The FCC regulations limit the field strength of 315 MHz alarm devices to a maximum average field strength.
One problem with presently available systems is that installations of such residential alarm systems may experience reception problems due to limitations in the range between the transmitters and receiver due to its low level of permissible field strength of RF transmissions.
In one prior arrangement a pulse width amplitude modulated scheme is used for transmission of data. In that arrangement, bits of data are not sent as contiguous bits. The individual bits are sent as bursts of carrier and for example a "1" might be twice the width of a "0" and there is no carrier between bits.