Back-up beeper

A back-up beeper, also known as back-up alarm or vehicle motion alarm, is a device intended to warn passers-by of a vehicle moving in reverse. Some models produce pure tone beeps at about 1000 Hz and 97-112 decibels.

Matsusaburo Yamaguchi of Yamaguchi Electric Company, Japan, invented the back-up beeper which was first manufactured as model BA1 in 1963.

In the U.S., the back-up beeper was first manufactured by Ed Peterson who sold the system to Boise engineering firm Morrison Knudsen in 1967. As of 1999, the company marketed the Bac-A-Larm and sold about one million of the backup alarms annually, more than other suppliers.

ISO 6165 describes "audible travel alarms", and ISO 9533 describes how to measure the performance of the alarms.