The start contact is often given with a pistol. In 1879, the bullet,
as it left the barrel, caused a plate to pivot, releasing a counterweight which,
as it fell, broke Muybridge's
thread. In 1880, Dr. McLoad placed an electric contact in front of the gun-
barrel. This approach was correct in theory but not very practicable because
of the flame and the powder expelled by the cartridge.
For many years, the opposite approach was adopted. The contact was placed in the butt of the gun. The method was very reliable but less precise. Today, indeed since the 'seventies, pressure transducers, separate from the pistol, are used which are accurate to within a thousandth of a second. The individual loud-speaker for each athlete was introduced at the Olympic Games in Mexico in 1968. The validity of starts is often measured by human reactions time .
The two most classic examples are Dragster races in the USA and track competition. Human reaction time is twofold. There is the reflex time which is the lapse of time between a stimulus somewhere on the body and the cry of paint. Then there is the interpretation time, which follows the opposite path and which we call reaction time. It is this that is checked and which will determine whether or not there has been a false start.
It was in 1972, for the Olympic Games in Munich, that technicians from Junghans placed pressure detectors in the track starting blocks. In swimming, since the 'seventies, starting platforms with electric contacts have been in use. They allow officials to compare the validity of the changeovers in a relay event. But to implement this measurement, you need the other time, that provided by the contact plate. This was one of the last chronometric problems of any importance to be solved.