Paging system having a vehicle mounted repeater with a portable paging receiver detachably mounted thereon

Claim 1

A paging system comprising: a central radio station for collectively controlling said system; an on-board radio unit connected to said central radio station by a first channel to receive a first call signal and a voice message from said central radio station, said on-board radio unit being operable for transmitting information to said central radio station via said first channel; an on-board repeater electrically connected to said on-board radio unit and mounted on the same vehicle as said on-board radio unit, said on-board repeater having means for generating said information and for supplying said generated information to said on-board radio unit; and a portable unit removably mounted on said on-board repeater and, when removed from said repeater to be carried, connected to said repeater by a second channel which is different from said first channel, wherein said information generated by said on-board repeater and transmitted by said on-board radio to said central radio station comprises an absence answer signal indicating that said portable unit is not mounted on said on-board repeater, and a repeat start signal indicating that said on-board repeater has started transmitting said voice message to said portable unit via said second channel, and wherein said on-board repeater comprises: detector means for detecting whether or not said portable unit is mounted on said on-board repeater; signal generating means for generating said absence answer signal and said repeat start signal, and for generating a second call signal which is meant for said portable unit; and control means for, when said portable unit is not mounted on said on-board repeater, responding to a call receive signal, which said on-board radio unit produces in response to said first call signal, by controlling said signal generating means to send said absence answer signal and said repeat start signal to said on-board radio unit for transmission to said central radio station via said first channel while, at the same time, sending said second call signal to said portable unit, said control means also sending said voice message to said portable unit.