Tyer's Electric Train Tablet system is a form of railway signalling for single line railways used in several countries; it was first devised in Great Britain by engineer Edward Tyer after the Thorpe rail accident of 1874, which left 21 people dead. It was used in New Zealand for close to 100 years until June 1994.The system used a hard disk called a tablet, a form of token. With advances in electrical locking of the lever frame within the signal box, the tablet instrument also electrically locked the section signal lever. That was marked with a white stripe on the red background.