Smoke and fire detection system communication

A fire detection system of the kind in which a controller randomly sends outgoing data in the form of one-valued bits and zero-valued bits to a plurality of transponders via a communication line and said transponders return data to said controller via said communication line, said system comprising:

• circuitry associated with said controller including means for sending said outgoing data in the form of a succession of transponder identifying 13-bit words, each one-valued bit being represented by a first voltage level on said communication line, each zero-valued bit being represented by a second voltage level on said communication line, said 13-bit word including a nine-bit address, a 3-bit command word, and a parity bit, said circuitry including means for generating spacing signals between each one-valued bit or each zero-valued bit with each spacing signal represented by a third voltage level on said communication line and
• circuitry associated with each said transponder for returning data to said controller, following the receipt of each said 13-bit word, said data being returned in the form of a selected plurality of pulses, each represented by the drawing of current from said communication line for a period having a duration representative of a corresponding data value at a substantially constant line voltage.

A communication method for a calibratable fire detection system of the kind in which a plurality of transponders each sends data, via respective transmission circuitry, to a controller via a communication line, the method comprising:

• sending said data in the form of a group of data signals, each said data signal having a duration based on data presented to the respective transmission circuitry,
• presented to the respective transmission circuitry a reference value, intended to provide a reference signal, of a predetermined nominal duration at the controller, every said group of data signals being accompanied by a current said reference signal, and
• detecting the durations of said data signals and the duration of the associated said reference signal for use in calibration.

A communication method for use in a fire detection system of the kind in which a controller sends data, in the form of one-valued bits and zero-valued bits, to a plurality of transponders via a communication line and said transponders return data to said controller via said communication line, said method comprising:

• sending said data in the form of a succession of 13-bit words, each one-valued bit being represented by a first voltage level on said communication line, each zero-valued bit being represented by a second voltage level on said communication line, said 13-bit word including a nine-bit address, a 3-bit command word, and a parity bit, including spacing each bit from each adjacent bit by a spacing signal represented by a third voltage level different from said first and said second voltage levels and
• returning data to said controller, following the receipt of each said 13-bit word, said data being returned in the form of five pulses, each represented by the drawing of current from said communication line for a period having a duration representative of a corresponding data value.

A fire detection system of the kind in which a controller randomly sends outgoing data in the form of one-valued bits and zero-valued bits to a plurality of transponders via a communication line and said transponders return data to said controller via said communication line, said system comprising:

• means, associated with said controller, for sending said outgoing data in the form of a succession of transponder identifying words f a predetermined number of bits, each one-valued bit being represented by a first voltage level on said communication line, each zero-valued bit being represented by a second voltage level on said communication line, each said word including at least an address portion, and a command portion, said sending means including means for generating spacing signals between each one-valued bit or each zero-valued bit with each spacing signal represented by a third voltage level on said communication line and
• means, associated with each said transponder, for returning data to said controller, following the receipt of each said word, said data being returned in the form of a selected plurality of pulses, each represented by the drawing of current from said communication line for a period having a duration representative of a corresponding data value at a substantially constant line voltage.