The research undertaken by Davis and Shah employed a simple black and white camera, and a glove which is black, except for white fingertips. A four-state finite state machine was used to recognise a simple set of seven gestures that would be used in interaction with computers -- like left, right, up, down, rotate, grab, stop. The four states of the finite state machine were:
As can be seen, this is a very simple system, and it works quite well. However, it has some significant shortcomings for use in full sign language -- such as it does not monitor hand position, and requires explicit stop/start signals, and only operates at 4 Hz. Furthermore, the ``finite state machine'' approach is very limited and is really a ``posture'' recognition system rather than a ``gesture'' recognition system. The finite state machine has, in some of the experiments, gone prematurely into the wrong state, and in such situations, it is difficult to get it back into a correct state.