Cordless telephone system

Claim 1

A battery saving method in a base communication unit connected to a plurality of telephone lines and having the same number of radio transceivers as said telephone lines and a controller provided with a storage for controlling said transceivers, and portable communication units equal in number to said telephone lines and each being connected to a respective one of said transceivers of said base communication unit by a cordless communication link, said method comprising the steps of: (a) turning a power source of said base communication unit ON; (b) turning a power source of a first one of said portable communication units ON and sending a first portable unit power ON signal to the base communication unit; (c) in response to said first portable unit power ON signal, sending a predetermined battery saving (BS) period designate signal from the base communication unit to said first portable communication unit at a first timing while, at the same time, registering said first portable communication unit in said storage of said controller of said base communication unit; (d) in response to said BS period designate signal, causing the first portable communication unit to enter into a BS operation at a second timing and at a first period designated; (e) turning a power source of a second one of the portable communication units ON and sending a second portable unit power ON signal to the base communication unit; (f) in response to said second portable unit power ON signal, causing said base communication unit to send the BS period designate signal to said first and second portable communication units at a third and a fourth timing, respectively, while at the same time registering said first and second portable communication units in the storage of said base communication unit in an order of power source ON; (g) in response to said BS period designate signal, changing the first period to a second period designated so as to cause the first portable communication unit to perform a BS operation at a fifth timing and at a second period while, at the same time, causing the second portable communication unit to perform a BS operation at a sixth timing and said second period; and (h) applying said sequence of steps sequentially to a third one and onward of the portable communication units to cause said third portable communication unit and others individually perform BS operations.