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R.F. communication system interrogation apparatus and method

  • US 5,390,360 A
  • Filed: 11/17/1992
  • Issued: 02/14/1995
  • Est. Priority Date: 12/23/1991
  • Status: Expired due to Term
First Claim
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1. A communication system comprising a primary unit, first and second secondary units for communicating with the primary unit over a radio channel and tertiary units for communicating with the secondary units over the channel, whereinthe primary unit comprisesmeans for transmitting a command to initiate contention and interrogation,each secondary unit comprisesmeans for receiving said command to initiate contention and interrogation,delay means responsive to reception of said command for delaying for a period of time selected from a set of time delays,monitoring means for determining whether the channel is free,transmitting means for executing an interrogation cycle by transmitting to at least one of the tertiary units if the channel is still free at the end of the selected delay period,delay increase means for increasing the delay for the next transmission when an interrogation cycle is executed, anddelay decrease means for decreasing the delay for the next transmission when an interrogation cycle is not executed,and wherein the time delays of the set of time delays of the first and second secondary units are different.

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