What makes the speedo and rev counter on a Volvo v40 work?

The speedometer and rev counter (tachometer) on a Volvo V40 function through electronic signals generated by the vehicle's sensors. The speedometer receives data from the wheel speed sensor, which measures the rotation of the wheels, while the tachometer gets input from the engine control unit (ECU), which monitors engine RPM through the crankshaft position sensor. These signals are then processed and displayed on the dashboard gauges, providing real-time information to the driver.