English: Coherer radiotelegraphy receiver designed by the French inventor Auguste Jean-Baptiste Tauleigne (1870-1926) around 1914. This was used to receive radiotelegraphy text messages in from a spark-gap transmitter . The coherer which detected the radio signals from the wire antenna, a horizontal glass tube with metal powder between two electrodes, is visible at right. The radio signal caused the metal powder to become conductive, allowing current from a battery (not visible) to flow through it to register on the siphon recorder. The siphon recorder ( left ) recorded the Morse code as an ink line on a paper tape, which could be translated later into text by an operator. Alternately the code could be listened to using the headphones ( right ). A bell ( right ) was provided to alert the operator when a message was coming in.