In-vehicle receiver and tire air pressure monitoring system

A tire air pressure monitoring system for a vehicle having a plurality of wheels equipped with tires, the tire air pressure monitoring system comprising:

• a plurality of transmitters respectively disposed in each of the tires of the plurality of wheels and transmitting a frame having information related to a tire air pressure at a predetermined regular transmission period;
• and
• an in-vehicle receiver disposed on a body side of the vehicle, wherein:
• the in-vehicle receiver includes:
• an electric wave reception unit that receives the frame and a specific electric wave emitted by a mobile terminal;
• and
• a control unit that detects an occurrence of a decrease in the tire air pressure based on data related to the tire air pressure in the frame, wherein:
• the control unit switches to a specific mode in which the electric wave reception unit receives the specific electric wave at every predetermined first intermittent period while a starting switch of the vehicle is in an off state;
• and
• the control unit switches from the specific mode or a power saving mode to a monitoring mode in which the electric wave reception unit receives the frame at every predetermined second intermittent period to monitor the tire air pressure intermittently while the starting switch of the vehicle is in the off state.