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.
Early radio inventors used a variety of methods to detect radio waves. Those early detectors tended to be slow and cumbersome in operation and that limited transmission speed. In 1906, Lee de Forest built on the work of Thomas Edison and John Ambrose Fleming and invented an electron tube he called an “Audion.” His tube contained three internal elements: a filament, an electrode and a control grid. Today we call tubes of this type “triodes.” In 1907 De Forest received U.S. Patent #841,387 for his invention, one of the most important in the history of radio.
Telegraph relays amplify an electrical signal in a telegraph line. Telegraph messages travel as a series of electrical pulses through a wire from a transmitter to a receiver. The pulses fade in strength as they travel through the wire, limiting the distance a message can be sent. Relays remedy that problem by detecting a weak signal and automatically re-transmitting that signal down the line using a local power source.
Telegraph relays amplify an electrical signal in a telegraph line. Telegraph messages travel as a series of electrical pulses through a wire from a transmitter to a receiver. The pulses fade in strength as they travel through the wire, limiting the distance a message can be sent. Relays remedy that problem by detecting a weak signal and automatically re-transmitting that signal down the line using a local power source.
Telegraph keys are electrical on-off switches used to send messages in Morse code. The Mecograph Company created a right-angle semi-automatic telegraph key around 1906. They competed with Horace Martin's Vibroplex Company until Martin purchased Mecograph in 1914. A semi-automatic key repeated the Morse code dots rapidly, much like holding down a key on a keyboard for repeated letters. The operator still keyed the dashes but could work much faster.
Telegraph relays amplify an electrical signal in a telegraph line. Telegraph messages travel as a series of electrical pulses through a wire from a transmitter to a receiver. The pulses fade in strength as they travel through the wire, limiting the distance a message can be sent. Relays remedy that problem by detecting a weak signal and automatically re-transmitting that signal down the line using a local power source.
Telegraph relays amplify an electrical signal in a telegraph line. Telegraph messages travel as a series of electrical pulses through a wire from a transmitter to a receiver. The pulses fade in strength as they travel through the wire, limiting the distance a message can be sent. Relays remedy that problem by detecting a weak signal and automatically re-transmitting that signal down the line using a local power source.
Telegraph relays amplify an electrical signal in a telegraph line. Telegraph messages travel as a series of electrical pulses through a wire from a transmitter to a receiver. The pulses fade in strength as they travel through the wire, limiting the distance a message can be sent. Relays remedy that problem by detecting a weak signal and automatically re-transmitting that signal down the line using a local power source.
Telegraph keys are electrical on-off switches used to send messages in Morse code. The message travels as a series of electrical pulses through a wire. The operator moves this key’s lever from side to side to make signals. Called a simplex-duplex key, this key can send messages either on one-way circuits (simplex) or on circuits designed to send messages on lines designed to carry two messages at once (duplex.)
This telegraph register was made by Charles Chester of New York and displays the design typical of the mid 19th Century. Telegraph registers are electrically-activated printers that receive Morse code messages. The message travels as a series of electrical pulses through a wire. The pulses energize the register’s electromagnets which move a lever-arm holding a pen or stylus. A clockwork mechanism pulls a strip of paper across the pen or stylus, recording the message. Short pulses draw or emboss a dot, slightly longer pulses a dash. The sequence of dots and dashes represent letters and numbers.
Leyden jars were essential for storing electrical charges used by the earliest wireless radios used aboard ocean liners. Shortly after RMS Carpathia's rescue of Titanic survivors, the ship visited Boston, Massachusetts. Marconi Wireless Radio employee Harry Cheetham boarded Carpathia to service the radio, which had been damaged during the Titanic operations. He replaced these two Leyden jars. One is intact and the other is broken, but fortunately the broken one shows how the jars were constructed inside to store and relay an electrical charge. Cheetham kept these artifacts as Titanic souvenirs, and donated them to the Smithsonian in 1930.
Telegraph relays amplify an electrical signal in a telegraph line. Telegraph messages travel as a series of electrical pulses through a wire from a transmitter to a receiver. The pulses fade in strength as they travel through the wire, limiting the distance a message can be sent. Relays remedy that problem by detecting a weak signal and automatically re-transmitting that signal down the line using a local power source.
Telegraph relays amplify an electrical signal in a telegraph line. Telegraph messages travel as a series of electrical pulses through a wire from a transmitter to a receiver. The pulses fade in strength as they travel through the wire, limiting the distance a message can be sent. Relays remedy that problem by detecting a weak signal and automatically re-transmitting that signal down the line using a local power source.
One of two telephones used by Alexander Graham Bell in a demonstration that took place between Boston and Salem, Massachusetts on November 26, 1876. Critical features are the iron diaphragm (seen as a black circular disc mounted on the vertical wooden support), two electromagnets (seen in white, facing the diaphragm) and a horseshoe permanent magnet (lying horizontal, pressed against the electromagnets).
When used as a transmitter, sound waves at the mouthpiece cause the diaphragm to move, inducing a fluctuating current in the electromagnets. This current is conducted over wires to a similar instrument, acting as a receiver. There, the fluctuating current in the electromagnets causes the diaphragm to move, producing air vibrations that can be heard by the ear. This was a marginal arrangement, but it worked well enough to be employed in the first commercial services in 1877. The magneto receiver continued to be used, but the transmitters were soon replaced by a carbon variable-resistance device designed by Francis Blake and based on a principle patented by Thomas Edison.
Telegraph relays amplify an electrical signal in a telegraph line. Telegraph messages travel as a series of electrical pulses through a wire from a transmitter to a receiver. The pulses fade in strength as they travel through the wire, limiting the distance a message can be sent. Relays remedy that problem by detecting a weak signal and automatically re-transmitting that signal down the line using a local power source.
Telegraph keys are electrical switches used to send coded messages that travel as a series of electrical pulses through a wire. Due to special difficulties in sending pulses through long underwater cables, so-called double-current keys were used. Instead of the short dots and long dashes of land-line telegraphs, submarine telegraphs sent positive pulses and negative pulses that made the receiver move right or left. The operator pressed one lever on the key to send a positive pulse and another to send a negative pulse. The code consisted of the sequence of left and right movements recorded on a paper tape. One knob is missing from this specimen.
Telegraph relays amplify an electrical signal in a telegraph line. Telegraph messages travel as a series of electrical pulses through a wire from a transmitter to a receiver. The pulses fade in strength as they travel through the wire, limiting the distance a message can be sent. Relays remedy that problem by detecting a weak signal and automatically re-transmitting that signal down the line using a local power source.
Telegraph relays amplify an electrical signal in a telegraph line. Telegraph messages travel as a series of electrical pulses through a wire from a transmitter to a receiver. The pulses fade in strength as they travel through the wire, limiting the distance a message can be sent. Relays remedy that problem by detecting a weak signal and automatically re-transmitting that signal down the line using a local power source.
Telegraph relays amplify an electrical signal in a telegraph line. Telegraph messages travel as a series of electrical pulses through a wire from a transmitter to a receiver. The pulses fade in strength as they travel through the wire, limiting the distance a message can be sent. Relays remedy that problem by detecting a weak signal and automatically re-transmitting that signal down the line using a local power source.