Telegraph relays amplified electrical signals in a telegraph line. Telegraph messages traveled as a series of electrical pulses through a wire from a transmitter to a receiver. Short pulses made a dot, slightly longer pulses a dash. The pulses faded in strength as they traveled through the wire, to the point where the incoming signal was too weak to directly operate a receiving sounder or register. A relay detected a weak signal and used a battery to strengthen the signal so that the receiver would operate.
This relay includes a marble base and was made by Charles T. Chester of New York City. The electromagnet coils are fixed but the steel core can be moved to adjust the strength of the magnetic field.
Telegraph relays amplified electrical signals in a telegraph line. Telegraph messages traveled as a series of electrical pulses through a wire from a transmitter to a receiver. Short pulses made a dot, slightly longer pulses a dash. The pulses faded in strength as they traveled through the wire, to the point where the incoming signal was too weak to directly operate a receiving sounder or register. A relay detected a weak signal and used a battery to strengthen the signal so that the receiver would operate.
“Main line” relays like this Western Electric unit were one of the most common types of relay and, as seen in this piece, were typically made with a resistance of 150 ohms. As the name suggests, main line relays served on major intercity circuits several hundred miles long. Better known for their Bell System telephone equipment, Western Electric manufactured a wide range of electrical devices.
Telegraph relays amplified electrical signals in a telegraph line. Telegraph messages traveled as a series of electrical pulses through a wire from a transmitter to a receiver. Short pulses made a dot, slightly longer pulses a dash. The pulses faded in strength as they traveled through the wire, to the point where the incoming signal was too weak to directly operate a receiving sounder or register. A relay detected a weak signal and used a battery to strengthen the signal so that the receiver would operate.
This distinctive-looking relay was known as a “clockface pole-changer” and was designed for use on polar duplex circuits powered by wet-cell batteries. Duplex circuits allowed for simultaneous transmission of two messages on the same line. The circuit design was such that operators could not tell which pole of the battery at a distant station might be on line and mismatched polarities interfered with reception. The clockface pole-changer could switch the polarity of the battery at the receiving station to eliminate the problem. This particular relay was inspected by "RH" of Wesern Union on 28 August 1917 and found to be "ok" with a resistance of 6.04 ohms.
Telegraph relays amplified electrical signals in a telegraph line. Telegraph messages traveled as a series of electrical pulses through a wire from a transmitter to a receiver. Short pulses made a dot, slightly longer pulses a dash. The pulses faded in strength as they traveled through the wire, to the point where the incoming signal was too weak to directly operate a receiving sounder or register. A relay detected a weak signal and used a battery to strengthen the signal so that the receiver would operate.
“Main line” relays like this Western Electric unit were one of the most common types of relay and, as seen in this piece, were typically made with a resistance of 150 ohms. As the name suggests, main line relays served on major intercity circuits several hundred miles long. Better known for their Bell System telephone equipment, Western Electric manufactured a wide range of electrical devices.
Telegraph relays amplified electrical signals in a telegraph line. Telegraph messages traveled as a series of electrical pulses through a wire from a transmitter to a receiver. Short pulses made a dot, slightly longer pulses a dash. The pulses faded in strength as they traveled through the wire, to the point where the incoming signal was too weak to directly operate a receiving sounder or register. A relay detected a weak signal and used a battery to strengthen the signal so that the receiver would operate.
Relays required adjustment to compensate for changing conditions on the line. Older designs used adjusting screws and springs to change the position of the coils and the sensitivity of the armature–a tricky task. Polarized or “polar” relays like this unit used a special coil-mount to eliminate the springs and coil adjusters. The coils were mounted to one end of a permanent magnet and the armature connected to the other end, so the coils and the armature had opposite magnetic polarity. Without an incoming signal the armature, attracted equally by both coils, sat balanced between them. The coils were wound in such a way that an incoming signal reinforced the magnetic field of one coil and reduced the field in the other, attracting the armature to one side to make contact and activate the relay.
Telegraph relays amplified electrical signals in a telegraph line. Telegraph messages traveled as a series of electrical pulses through a wire from a transmitter to a receiver. Short pulses made a dot, slightly longer pulses a dash. The pulses faded in strength as they traveled through the wire, to the point where the incoming signal was too weak to directly operate a receiving sounder or register. A relay detected a weak signal and used a battery to strengthen the signal so that the receiver would operate.
Box relays were most often used by linemen or station operators for testing purposes or where a local battery was not available. The covering box acted as a resonator that amplified the sound of the relay’s light-weight armature, making the signal audible without a sounder. This unusual miniature unit was made by the donor and was reportedly used briefly on the line between Pittsburgh and Baltimore.
Telegraph relays amplified electrical signals in a telegraph line. Telegraph messages traveled as a series of electrical pulses through a wire from a transmitter to a receiver. Short pulses made a dot, slightly longer pulses a dash. The pulses faded in strength as they traveled through the wire, to the point where the incoming signal was too weak to directly operate a receiving sounder or register. A relay detected a weak signal and used a battery to strengthen the signal so that the receiver would operate.
This pole-changing relay includes a plate citing "F. W. Jones Patents / April 17, 1888 / April 29, 1890." The citation refers to US Patents 381,251 and 426,819, respectively. Francis W. Jones of New York City received these patents for his inventions related to improvements in operating duplex and quadruplex telegraph devices on "dynamo machines" rather than primary batteries.
Telegraph relays amplified electrical signals in a telegraph line. Telegraph messages traveled as a series of electrical pulses through a wire from a transmitter to a receiver. Short pulses made a dot, slightly longer pulses a dash. The pulses faded in strength as they traveled through the wire, to the point where the incoming signal was too weak to directly operate a receiving sounder or register. A relay detected a weak signal and used a battery to strengthen the signal so that the receiver would operate.
“Main line” relays like this unit made by J. H. Bunnell & Co. were one of the most common types of relay and were typically made with a resistance of 150 ohms. As the name suggests, main line relays served on major intercity circuits several hundred miles long. This particular unit is rated for 200 ohms, a somewhat higher than normal resistance. A notation in the record refers to this relay as "R.R. Pattern". Presumably that means the piece was made or used specifically for railroad telegraph lines but the exact meaning is unclear.
Telegraph relays amplified electrical signals in a telegraph line. Telegraph messages traveled as a series of electrical pulses through a wire from a transmitter to a receiver. Short pulses made a dot, slightly longer pulses a dash. The pulses faded in strength as they traveled through the wire, to the point where the incoming signal was too weak to directly operate a receiving sounder or register. A relay detected a weak signal and used a battery to strengthen the signal so that the receiver would operate.
So-called “pony” relays like this unit made by Western Electric serviced private lines and shorter branch circuits. The resistance of a given pony relay varied depending on the length of the circuit. This 20 ohm pony relay would have been used on circuits up to about 15 miles in length.
Telegraph relays amplified electrical signals in a telegraph line. Telegraph messages traveled as a series of electrical pulses through a wire from a transmitter to a receiver. Short pulses made a dot, slightly longer pulses a dash. The pulses faded in strength as they traveled through the wire, to the point where the incoming signal was too weak to directly operate a receiving sounder or register. A relay detected a weak signal and used a battery to strengthen the signal so that the receiver would operate.
So-called “pony” relays like this unit made by J. H. Bunnell & Co., serviced private lines and shorter branch circuits. The resistance of a given pony relay varied depending on the length of the circuit. This 50 ohm pony relay would have been used on circuits up to about 45 miles in length.
Telegraph relays amplified electrical signals in a telegraph line. Telegraph messages traveled as a series of electrical pulses through a wire from a transmitter to a receiver. Short pulses made a dot, slightly longer pulses a dash. The pulses faded in strength as they traveled through the wire, to the point where the incoming signal was too weak to directly operate a receiving sounder or register. A relay detected a weak signal and used a battery to strengthen the signal so that the receiver would operate.
Relays required adjustment to compensate for changing conditions on the line. Older designs used adjusting screws and springs to change the position of the coils and the sensitivity of the armature–a tricky task. Polarized or “polar” relays like this unit made by J. H. Bunnell & Co., used a special coil-mount to eliminate the springs and coil adjusters. The coils were mounted to one end of a permanent magnet and the armature connected to the other end, so the coils and the armature had opposite magnetic polarity. Without an incoming signal the armature, attracted equally by both coils, sat balanced between them. The coils were wound in such a way that an incoming signal reinforced the magnetic field of one coil and reduced the field in the other, attracting the armature to one side to make contact and activate the relay.
Telegraph repeaters amplified electrical signals in a telegraph line. Telegraph messages traveled as a series of electrical pulses through a wire from a transmitter to a receiver. Short pulses made a dot, slightly longer pulses a dash. The pulses faded in strength as they traveled through the wire, limiting the distance a message could travel. Repeaters remedied that problem by detecting a weak signal and using a local power source to re-energize and re-transmit the signal down the line.
This working model was submitted to the U.S. Patent Office by inventor Elisha Gray of Chicago along with his patent application. On 16 May 1871, he received patent #114938 for his "Improvement in Telegraph-Repeaters." Gray's idea, called a "shunt repeater," transferred or "shunted" some of the electrical current to an extra pair of small electromagnets to allow for automatic operation of the repeater. Our records also associate this object with telegraph inventor Charles Haskins although the association is unclear. While Haskins did patent his own repeater whose action was described at the time as "similar to Gray's," patent 114938 was issued to Gray alone and was not assigned to anyone else.
Telegraph repeaters amplified electrical signals in a telegraph line. Telegraph messages traveled as a series of electrical pulses through a wire from a transmitter to a receiver. Short pulses made a dot, slightly longer pulses a dash. The pulses faded in strength as they traveled through the wire, limiting the distance a message could travel. Repeaters remedied that problem by detecting a weak signal and using a local power source to re-energize and re-transmit the signal down the line.
George F. Milliken, manager of the Boston office of Western Union, introduced a new type of automatic telegraph repeater in 1864 designed to remedy a defect in prior models. Sometimes a delay in energizing one electromagnet in a repeater resulted in a lever being held by another electromagnet too tightly for the springs to release. An operator had to send a dot at just the right time to activate the repeater. Milliken used an auxiliary magnet and added a mechanical linkage to solve the problem. Franklin Pope wrote in 1868, “One of the principal advantages in the construction of Milliken's repeater consists in the fact that any slight variation in the strength of the extra local circuit, from weakness of the battery or other causes, does not affect the adjustment of the relay magnets.... The adjustment and action of the two magnets are entirely independent of each other, .... The relay levers also move more freely, being unencumbered with extra armatures or other appliances.” Charles Davis and Frank Rae wrote almost ten years later that Milliken’s repeater, “is more simple in principle and much easier adjusted.” Western Union adopted the distinctive looking “Milliken repeater” as a standard piece of equipment and the term became generic. This unit bears the stamp of George M. Phelps and was presumably modified by Western Union engineer and inventor.
Telegraph relays amplified electrical signals in a telegraph line. Telegraph messages traveled as a series of electrical pulses through a wire from a transmitter to a receiver. Short pulses made a dot, slightly longer pulses a dash. The pulses faded in strength as they traveled through the wire, to the point where the incoming signal was too weak to directly operate a receiving sounder or register. A relay detected a weak signal and used a battery to strengthen the signal so that the receiver would operate.
This unusual looking relay bears the stamp of Charles T. Chester of New York. Charles and his brother John ran a business manufacturing electrical devices from 1855 to the latter's death in 1871. Charles patented several devices including improvements for batteries however we have not been able to associate a patent with this relay. The unit itself is a production piece with serial number 326.
Telegraph repeaters amplified electrical signals in a telegraph line. Telegraph messages traveled as a series of electrical pulses through a wire from a transmitter to a receiver. Short pulses made a dot, slightly longer pulses a dash. The pulses faded in strength as they traveled through the wire, limiting the distance a message could travel. Repeaters remedied that problem by detecting a weak signal and using a local power source to re-energize and re-transmit the signal down the line.
For many years inventors were required to submit models to the Patent Office when they filed for a patent. In 1856, Moses G. Farmer received U. S. patent #14,157 for his “telegraphic repeater”. This is the model Farmer submitted that shows his circuit for an improved way to retransmit telegraph signals. Prior to this invention repeaters had to be switched manually by a telegraph operator. This sometimes led to delays if the operator were otherwise occupied. Farmer's invention allowed for automatic operation of the repeater.
Telegraph relays amplified electrical signals in a telegraph line. Telegraph messages traveled as a series of electrical pulses through a wire from a transmitter to a receiver. Short pulses made a dot, slightly longer pulses a dash. The pulses faded in strength as they traveled through the wire, to the point where the incoming signal was too weak to directly operate a receiving sounder or register. A relay detected a weak signal and used a battery to strengthen the signal so that the receiver would operate.
This duplex relay was made by Charles Williams, Jr. of Boston and used in experiments by Moses Farmer. Duplex relays operated in a system designed to send two messages simultaneously over the same wire. Williams had made duplex devices for Joseph Stearns who devised the first practical duplex system in 1868 and also made early telephone devices for Alexander Graham Bell.
Telegraph relays amplified electrical signals in a telegraph line. Telegraph messages traveled as a series of electrical pulses through a wire from a transmitter to a receiver. Short pulses made a dot, slightly longer pulses a dash. The pulses faded in strength as they traveled through the wire, to the point where the incoming signal was too weak to directly operate a receiving sounder or register. A relay detected a weak signal and used a battery to strengthen the signal so that the receiver would operate.
This telegraph relay was intended for use on duplex telegraph circuits that allowed two messages to travel simultaneously on the same wire. A note found with the unit refers to this as a "Steiner" telegraph transmitter. Josef Steiner's patents were typically assigned to Western Union so this object likely reflects one of his improvements.
Telegraph relays amplified electrical signals in a telegraph line. Telegraph messages traveled as a series of electrical pulses through a wire from a transmitter to a receiver. Short pulses made a dot, slightly longer pulses a dash. The pulses faded in strength as they traveled through the wire, to the point where the incoming signal was too weak to directly operate a receiving sounder or register. A relay detected a weak signal and used a battery to strengthen the signal so that the receiver would operate.
Relays required adjustment to compensate for changing conditions on the line. Older designs used adjusting screws and springs to change the position of the coils and the sensitivity of the armature–a tricky task. Polarized relays like this unit made by electrical inventor Moses Farmer used a special coil-mount to eliminate the springs and coil adjusters. The coils were mounted to one end of a permanent magnet and the armature connected to the other end, so the coils and the armature had opposite magnetic polarity. Without an incoming signal the armature, attracted equally by both coils, sat balanced between them. The coils were wound in such a way that an incoming signal reinforced the magnetic field of one coil and reduced the field in the other, attracting the armature to one side to make contact and activate the relay.
Telegraph relays amplified electrical signals in a telegraph line. Telegraph messages traveled as a series of electrical pulses through a wire from a transmitter to a receiver. Short pulses made a dot, slightly longer pulses a dash. The pulses faded in strength as they traveled through the wire, to the point where the incoming signal was too weak to directly operate a receiving sounder or register. A relay detected a weak signal and used a battery to strengthen the signal so that the receiver would operate.
“Main line” relays like this unit were common. Typically made with a resistance of 150 ohms, main line relays served on major intercity circuits. According to George C. Maynard, the curator who collected this piece in 1891, "This specimen seems to be a very slightly modified version of the Western Union Relay No. 2 of the Tillotson Company which was introduced in a 150 Ohms model about 1880-1881 at $8.50. As late as 1893 the E. S. Greeley Co. was still using the Tillotson illustration of 1880-1881. However the caption had been changed to 'Improved Western Union Relay'. ... The armature or lever in this model is the old style of two-piece construction. A bar across the poles of the magnet is attached to the lever [instead of a single-piece lever]."
Telegraph relays amplified electrical signals in a telegraph line. Telegraph messages traveled as a series of electrical pulses through a wire from a transmitter to a receiver. Short pulses made a dot, slightly longer pulses a dash. The pulses faded in strength as they traveled through the wire, to the point where the incoming signal was too weak to directly operate a receiving sounder or register. A relay detected a weak signal and used a battery to strengthen the signal so that the receiver would operate.
This telegraph repeater was made by Western Electric Manufacturing Company in Chicago. Better know for their long association with the Bell Telephone System, they also fabricated other electrical devices. The theory and operation of telegraph systems constituted a part of standard physics and electrical engineering curricula in the late 19th and early 20th centuries, as at Oberlin College. The Physics Department at that school donated this repeater to the new National Museum of History and Technology in 1964.