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Cordless key telephone system for covering multiple service areas having exclusively assigned control channels

  • US 5,283,817 A
  • Filed: 04/17/1991
  • Issued: 02/01/1994
  • Est. Priority Date: 04/17/1990
  • Status: Expired due to Fees
First Claim
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1. A cordless key telephone system for covering a plurality of service areas, wherein a frequency spectrum of radio signals used by said system is equally divided into a plurality of channels of equal bandwidth, comprising:

  • a plurality of access units divided into groups corresponding respectively to said service areas, the access units of each group being located in the corresponding service area for broadcasting radio signals on a two-way control channel or on an assigned two-way speech channel, the access units of each group having a uniquely assigned control channel different in a frequency from the control channel of the other group;

    a plurality of cordless stations for exchanging radio signals with said access units, said cordless stations being respectively identified by unique station identifiers, each of said cordless stations being sequentially switchable to the control channel of one of said groups and to the control channel of the other group; and

    a main controller coupled to a switched telephone network for selecting one of the access units for each of said service areas in response to an incoming call from said network and transmitting a first alert signal to the selected access units;

    each of said access units comprising alert signal generator means for generating a recurrent sequence of second alert signals respectively containing the identifiers of standby cordless stations, and control means responsive to said first alert signal for activating said alert signal generator means to broadcast said recurrent sequence of said second alert signals, said control means being further responsive to receipt of an acknowledgment signal from one of said cordless stations for transmitting a copy of the acknowledgment signal to said main controller, responsive to receipt of a proceed-to-assign signal from said main controller for deactivating said alert signal generator means, for broadcasting a channel assignment signal indicating an assigned speech channel and for switching the access unit to the assigned speech channel, responsive to receipt of an end-of-switching signal from one of the cordless station for sequentially broadcasting ringing signals respectively containing the identifiers of the cordless stations which returned said first acknowledgement signals, responsive to receipt of an off-hook signal from one of the cordless stations for transmitting a copy of the off-hook signal to said main controller, and responsive to receipt of a turn-on signal from said main controller containing the identifier of a cordless station going off hook for broadcasting a copy of said turn-on signal,said main controller comprising means for transmitting said turn-on signal to one of the selected access units if said copy of the off-hook signal is received therefrom, andeach of said cordless stations comprising means for transmitting said acknowledgment signal if the second alert signal containing the identifier of the station is detected in one of the sequentially switched control channels, switching the cordless station to the assigned channel in response to said channel assignment signal, transmitting said end-of-switching signal in response to the cordless station being switched to the assigned channel, transmitting said off-hook signal when the cordless station goes off hook in response to the ringing signal having the identifier of the station, and activating a speech circuit in response to receipt of said broadcast copy of the turn-on signal containing the identifier of the station,wherein odd-numbered ones of said divided channels are assigned to the access units of a first one of said groups as speech channels and an even-numbered one of said channels is assigned to the first group access units as a first control channel, and even-numbered ones of said channels are assigned to the access units of a second one of said groups as speech channels and an odd-numbered one of said channels is assigned to the second group access units as a second control channel, said first control channel being excluded from the speech channels assigned to the second group access units and said second control channel being excluded from the speech channels assigned to the first group access units.

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