1. An automatic centralized monitoring system capable of monitoring various functions in a plurality of premises: comprising, a central station, said premises being adapted to be linked to said central station, monitoring means comprising one or more sensors adapted to be located in each of said premises, a plurality of m line driver means located at said central station linked to said premises, said premises being arranged in m unique groups with each group having a capacity of n premises, (m and n each being integers greater than one), each of the m line driver means being connected to a respective one of the unique groups, said line driver means being controlled by a computer means which is arranged to cause all the line driver means to: (a) simultaneously select a predetermined first one of each of the n premises of its respective group of premises; (b) read the sensor, or sensors, at each of the predetermined premises simultaneously, multiplex the readings, and transmit the multiplexed readings from all of the line driver means to the computer which can then rapidly interpret the received readings; (c) simultaneously select a predetermined second one of the n premises of its respective group of premises, and repeat the process of "b;" (d) continue to select an additional predetermined premise in each group in the manner described in a and b until all n premises have been interrogated, whereby the total time of scanning and interpreting is made short by using the speed of the computer for demultiplexing and interpreting.