page_title: Ambrose Channel pilot cable
section_title: Description and operation
hierarchical_section_title: Ambrose Channel pilot cable / Description and operation
caption_attribution_description: English: A 1921 depiction of the layers of the Ambrose Channel pilot cable.
context_page_description: The Ambrose Channel pilot cable, also called the Ambrose Channel leader cable, was a cable laid in Ambrose Channel at the entrance to the Port of New York and New Jersey that provided an audio tone for guiding ships in and out of port at times of low visibility. The cable was laid during 1919 and 1920; it had been removed from the channel and replaced by wireless technology by the end of the 1920s.
context_section_description: The Ambrose leader cable was an armored cable with a single internal conductor (see picture) that acted like a long radio antenna laid on the channel floor. It originated at Fort Lafayette (near the present day Verrazano-Narrows Bridge), then extended 16 miles down the Ambrose Channel to the vicinity of Lightship Ambrose offshore.  It was powered by a generator at Fort Lafayette that produced 500 Hz (cycles per second) current at 400 volts, resulting in an alternating electromagnetic field along the length of the cable that could be detected to approximately a thousand yards away.  The current was mechanically keyed to send the word "NAVY" in Morse Code.
  A ship received by a pair of induction coils hung on opposite sides of the ship, and fed through an amplifier into a headset (see diagram, below). By switching between coils, the relative strength of the signal on each side could be compared. The ship maintained a course parallel to the cable by maneuvering to keep the signal strength constant.
caption: The Cable was composed of several layers.[3]
exif: {}