ZF TRW offers both basic and enhanced direct tire pressure monitoring systems (TPMS). The basic system alerts drivers when tires are underinflated through a warning light on the instrument panel. The enhanced system locates the underinflated tire(s) and displays individual warnings.

ZF TRW’s direct TPMS solutions comply with Federal regulations in the US, as well as European customer requirements. Keys to the system are a battery-powered remote frequency sensor that is deployed in each wheel, as well as a receiver that retrieves tire data from each of the four sensors.

Direct TPMS, unlike indirect TPMS, measures true tire pressure, so there are no error factors or inaccuracies due to calculating other indirect pressure measurements, such as wheel rotational speed.

More info here - http://www.trw.com/electronic_system...ure_monitoring