Patent ID: 7026953

Claim:
A keyless entry device having a tire pressure monitoring function comprising a portable unit, tire pressure transmitters which are respectively mounted on a plurality of tires and a mainunit, wherein the mainunit includes a plurality of antennas which receive high frequency signals from the portable unit and the tire pressure transmitters, a high frequency receiver which reproduces data from the high frequency signals received by the plurality of antennas, an intermittent controller which changes over operation of the high frequency receiver between continuous operation and intermittent operation in an interlocking manner with turning on or off of an ignition key of an automobile, and a data processor which outputs the data as control signals, wherein when the ignition key is turned on, the intermittent controller changes over operation of the high frequency receiver to continuous operation and the data processor outputs control signals in response to data from the tire pressure transmitters and does not output control signals in response to data from the portable unit, wherein when the ignition key is turned off, the intermittent controller changes over operation of the high frequency receiver to intermittent operation and the data processor outputs control signals in response to data from the portable unit, wherein the mainunit further includes an antenna changeover part, wherein when the intermittent controller changes over operation of the high frequency receiver to continuous operation, the antenna changeover part changes over a plurality of respective antennas from an OFF state to an ON state in sequence, and wherein when the intermittent controller changes over the high frequency receiver to intermittent operation, the antenna changeover part intermittently and simultaneously turns the plurality of antennas to the ON state in synchronism with the intermittent operation of the high frequency receiver.