Telegraph sounder
Encyclopedia
A telegraph sounder is a device which produces an audible sound when connected to an operating electrical telegraph
.
It is similar in form to a relay
.
When current flows through an electromagnet
, the resulting magnetic field
attracts an armature that is held up by a weight. When the current is switched on, the arm is pulled down to the electromagnet, resulting in a "click" When the current ends, the weight pulls the armature back to its resting position, resulting in a "clack." Thus, as the Telegraph key makes and breaks a contact, the sounder echoes the up and down state of the key.
It is important that a sounder makes a sound both when the circuit is broken and when it is restored. This eases the process of identifying long and short presses of the key to send characters in morse code
.
It is important that one does not confuse this with CW
The default condition of the telegraph circuit is with electricity flowing. This enables the operator to easily detect a fault in the wire.
Electrical telegraph
An electrical telegraph is a telegraph that uses electrical signals, usually conveyed via telecommunication lines or radio. The electromagnetic telegraph is a device for human-to-human transmission of coded text messages....
.
It is similar in form to a relay
Relay
A relay is an electrically operated switch. Many relays use an electromagnet to operate a switching mechanism mechanically, but other operating principles are also used. Relays are used where it is necessary to control a circuit by a low-power signal , or where several circuits must be controlled...
.
When current flows through an electromagnet
Electromagnet
An electromagnet is a type of magnet in which the magnetic field is produced by the flow of electric current. The magnetic field disappears when the current is turned off...
, the resulting magnetic field
Magnetic field
A magnetic field is a mathematical description of the magnetic influence of electric currents and magnetic materials. The magnetic field at any given point is specified by both a direction and a magnitude ; as such it is a vector field.Technically, a magnetic field is a pseudo vector;...
attracts an armature that is held up by a weight. When the current is switched on, the arm is pulled down to the electromagnet, resulting in a "click" When the current ends, the weight pulls the armature back to its resting position, resulting in a "clack." Thus, as the Telegraph key makes and breaks a contact, the sounder echoes the up and down state of the key.
It is important that a sounder makes a sound both when the circuit is broken and when it is restored. This eases the process of identifying long and short presses of the key to send characters in morse code
Morse code
Morse code is a method of transmitting textual information as a series of on-off tones, lights, or clicks that can be directly understood by a skilled listener or observer without special equipment...
.
It is important that one does not confuse this with CW
Continuous wave
A continuous wave or continuous waveform is an electromagnetic wave of constant amplitude and frequency; and in mathematical analysis, of infinite duration. Continuous wave is also the name given to an early method of radio transmission, in which a carrier wave is switched on and off...
The default condition of the telegraph circuit is with electricity flowing. This enables the operator to easily detect a fault in the wire.
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.)