Postal tube system slug arrangement - used for testing purposes with buzzer for easy location from outside

摘要

The slug is for use in a postal tube system as a test slug. It either emits a signal detectable from outside with or without the aid of auxiliary equipment, or is so designed that it can be located from outside. The design allows the position of any jam to be rapidly located. In its simplest form the slug can have a battery-operated siren or buzzer audible from outside, or it can incorporate a radio or ultrasonic transmitter. A further alternative is to make it so that it can be located by a metal detector.