Because every person's fingerprint, iris, voice, retina face, hand, vein and signature are unique, a biometric time clock provides a quick, accurate, and reliable way to record "In" and "Out" punches for each employee. The most common, reliable and successful system is the one based on Finger Prints. Users are supposed to put their thumb/index finger (or any specified finger) in the finger reader. The system then compares the finger print that is read with that in the central database for authentication. Most of the Biometric Systems do not keep an image of the fingerprint but a template.