A telegraph sounder is an antique

electromechanical In engineering, electromechanics combines processes and procedures drawn from electrical engineering and mechanical engineering. Electromechanics focuses on the interaction of electrical and mechanical systems as a whole and how the two systems ...

device used as a receiver on

electrical telegraph Electrical telegraphs were point-to-point text messaging systems, primarily used from the 1840s until the late 20th century. It was the first electrical telecommunications system and the most widely used of a number of early messaging systems ...

lines during the 19th century. It was invented by

Alfred Vail Alfred Lewis Vail (September 25, 1807 – January 18, 1859) was an American machinist and inventor. Along with Samuel Morse, Vail was central in developing and commercializing American telegraphy between 1837 and 1844. Vail and Morse were the f ...

after 1850 to replace the previous receiving device, the cumbersome Morse register and was the first practical application of the

electromagnet An electromagnet is a type of magnet in which the magnetic field is produced by an electric current. Electromagnets usually consist of wire wound into a coil. A current through the wire creates a magnetic field which is concentrated in the ...

. When a telegraph message comes in it produces an audible "clicking" sound representing the short and long keypresses – "dots" and "dashes" – which are used to represent text characters in

Morse code Morse code is a method used in telecommunication to encode text characters as standardized sequences of two different signal durations, called ''dots'' and ''dashes'', or ''dits'' and ''dahs''. Morse code is named after Samuel Morse, one of ...

. A

telegraph operator A telegraphist (British English), telegrapher (American English), or telegraph operator is an operator who uses a telegraph key to send and receive the Morse code in order to communicate by land lines or radio. During the Great War the Royal ...

would translate the sounds into characters representing the telegraph message.

Telegraph Telegraphy is the long-distance transmission of messages where the sender uses symbolic codes, known to the recipient, rather than a physical exchange of an object bearing the message. Thus flag semaphore is a method of telegraphy, whereas p ...

networks, used from the 1850s to the 1970s to transmit text messages long distances, transmitted information by pulses of current of two different lengths, called "dots" and "dashes" which spelled out text messages in

. A telegraph operator at the sending end of the line would create the message by tapping on a switch called a

telegraph key A telegraph key is a specialized electrical switch used by a trained operator to transmit text messages in Morse code in a telegraphy system. Keys are used in all forms of electrical telegraph systems, including landline (also called wire) t ...

, which rapidly connects and breaks the circuit to a

battery Battery most often refers to: * Electric battery, a device that provides electrical power * Battery (crime), a crime involving unlawful physical contact Battery may also refer to: Energy source *Automotive battery, a device to provide power t ...

, sending pulses of current down the line. The telegraph sounder was used at the receiving end of the line to make the Morse code message audible. Its simple mechanism was similar to a

relay A relay Electromechanical relay schematic showing a control coil, four pairs of normally open and one pair of normally closed contacts An automotive-style miniature relay with the dust cover taken off A relay is an electrically operated switch ...

. It consisted of an

attached to the telegraph line, with an iron armature near the magnet's pole balanced on a pivot, held up by a counterweight. When

current Currents, Current or The Current may refer to: Science and technology * Current (fluid), the flow of a liquid or a gas ** Air current, a flow of air ** Ocean current, a current in the ocean *** Rip current, a kind of water current ** Current (stre ...

flowed through the

's winding, it created a

magnetic field A magnetic field is a vector field that describes the magnetic influence on moving electric charges, electric currents, and magnetic materials. A moving charge in a magnetic field experiences a force perpendicular to its own velocity and to ...

which attracted the armature, pulling it down to the electromagnet, resulting in a "click" sound. When the current ended, the counterweight pulled the armature back up to its resting position, resulting in a "clack" sound. Thus, as the telegraph key at the sending end makes and breaks the contact, the sounder echoes the up and down state of the key. It was important that a sounder make a sound both when the circuit was broken and when it was restored. This was necessary for the operator clearly to distinguish the long and short keypresses – the "dashes" and "dots" – that make up the characters in

morse code Morse code is a method used in telecommunication to encode text characters as standardized sequences of two different signal durations, called ''dots'' and ''dashes'', or ''dits'' and ''dahs''. Morse code is named after Samuel Morse, one of ...

References

External links

Morse Telegraph Club, Inc.
(The Morse Telegraph Club is an international non-profit organization dedicated to the perpetuation of the knowledge and traditions of telegraphy.)

- A photo gallery of telegraph sounders from the 19th and 20th centuries {{DEFAULTSORT:Telegraph Sounder Telegraphy Telecommunications equipment Electromagnetic components Sound technology Sound production technology Analog circuits