telegraph relay
Date1890-1920
Inventory Number1997-1-0570
ClassificationTelegraph Relay
Subject
Maker
American Telephone and Telegraph Company
1885 - 2005
User
Department of Physics, Harvard University
founded 1884
Cultural Region
Place of Origin
Dimensions8.4 × 19.4 × 10.4 cm (3 5/16 × 7 5/8 × 4 1/8 in.)
Material
DescriptionTelegraph relay mounted on a base that consists of a brown rectangular piece of wood sitting on a black piece of metal. Two brown cylinders (an electromagnet) lie in the middle of the base, a metal plate connecting them in the back. A thick coil runs from the back plate into a metal knob with an adjustment dial on the end. A small metal cylinder, with a slit on top, stands on the base to the left of the knob.
In front, there is a piece of metal between the cylinders, on top of which stands a small cylinder with a screw with two adjustment dials on the end going through it. There is a movable black piece of metal in front of the magnet with a hook attached to it. A light spring is attached to the hook and extends through a hole in the middle of a bronze piece of metal in front. There is a piece of string on the end of the spring attaching it to a large knob with an adjustment dial on top. A screw with two adjustment dials runs through the two front pieces of metal. Three small metal cylinders, each with a slit on top, stand to the left of the spring, and three to the right.
In front, there is a piece of metal between the cylinders, on top of which stands a small cylinder with a screw with two adjustment dials on the end going through it. There is a movable black piece of metal in front of the magnet with a hook attached to it. A light spring is attached to the hook and extends through a hole in the middle of a bronze piece of metal in front. There is a piece of string on the end of the spring attaching it to a large knob with an adjustment dial on top. A screw with two adjustment dials runs through the two front pieces of metal. Three small metal cylinders, each with a slit on top, stand to the left of the spring, and three to the right.
Signedunderneath, on paper: Property of / AMERICAN TEL. & TEL. CO.
Inscribedon base: OHM
FunctionThis telegraphic instrument was used as control relay in Bridge Polar Duplex. It could be used to control the current flow between other telegraphic instruments and switchboards. When a current flowed through the magnet, it would attract the metal plate in front, which would in turn exert a force on the spring. When the current ceased to flow, the spring would return to its resting position. The effect was that of opening and closing a switch.
ProvenanceFrom the Department of Physics, Lyman Laboratory, Harvard University.
Burnell Telephone and Electric Company
Date: circa 1905
Object number: 1997-1-0571
U.S. Electrical Supplies
Date: 1910-1920
Object number: 1997-1-0578
