Device for monitoring and wirelessly indicating a pressure or a pressure change in pneumatic tires mounted on vehicles

Device for monitoring and wirelessly signaling a pressure, or a change in pressure, in pneumatic tires on vehicles comprising:

• a pressure sensor for measuring the pressure or the change in pressure;
• a transmitter for transmitting a signal derived from the measuring signal of the pressure sensor;
• a control circuit that activates the transmitter intermittently to submit said derived signal;
• a battery as current source;
• and a back-up capacitor connected in parallel to the battery;
• and
• wherein a controllable switching unit is provided which is so controlled such that the back-up capacitor is connected in parallel to the battery intermittently before the control circuit activates the transmitter and for a limited period of time during the transmitting operation of the transmitter.