
92 LIGHT AND HEAVY VEHICLE TECHNOLOGY
in the transmitter winding heats the bimetallic strip,
thereby causing it to bend and open the contacts. Since
this action immediately interrupts the supply of current,
the strip will cool and the contacts will close again to
restore the circuit. In reality, of course, the process is
being continually repeated such that the bimetallic strip
oscillates to provide pulses of electric current. However,
the effect of rising oil pressure on the transmitter
diaphragm is to press the contacts more firmly together,
so that their rate of oscillation is reduced. In other
words, the current pulses sensed by the indicato ...