Editing Teleprinter (section)

==Ways in which teleprinters were used==
Teleprinters could use a variety of different communication channels. These included a simple pair of wires, [[public switched telephone network]]s, dedicated non-switched telephone circuits (leased lines), [[switched communication network|switched networks]] that operated similarly to the public telephone network ([[telex]]), and radio and [[microwave]] links (telex-on-radio, or TOR). 

There were at least five major types of teleprinter networks:
* Exchange systems such as [[Telex]] and [[Telex#Teletypewriter eXchange|TWX]] created a real-time circuit between two machines, so that anything typed on one machine appeared at the other end immediately. US and UK systems had telephone dials, and prior to 1981 five [[North American Numbering Plan]] (NANPA) [[area codes]] were reserved for teleprinter use. German systems did "dialing" via the keyboard. Typed "chat" was possible, but because billing was by connect time, it was common to prepare messages in advance on [[Punched tape|paper tape]] and transmit them without pauses for typing.
* [[Leased line]] and [[radioteletype]] networks arranged in point-to-point and / or multipoint configurations supported [[data processing]] applications for government and industry, such as integrating the accounting, billing, management, production, purchasing, sales, shipping and receiving departments within an organization to speed internal communications.
* [[Message switching]] systems were an early form of E-mail, using electromechanical equipment. See [[Telegram]], [[Western Union]], [[Plan 55-A]]. Military organizations had similar but separate systems, such as [[Autodin]].
* Broadcast systems such as weather information distribution and "news wires", which were received on "wire machines".<ref>{{Cite web |title=AP teletype machine |url=https://history.capitolbroadcasting.com/media-assets/ap-teletype-machine/ |access-date=2022-03-05 |website=CBC History |language=en-US}}</ref> Examples were operated by [[Associated Press]], [[National Weather Service]], [[Reuters]], and United Press (later [[UPI]]). Information was printed on receive-only teleprinters, without keyboards or dials.
* "Loop" systems, where anything typed on any machine on the loop printed on all the machines. American police departments used such systems to interconnect precincts.<ref>{{cite patent |title=Signaling system |status=Patent |country=US |number=2364357 |gdate=29 March 1944}}</ref>

Before the [[computer revolution]] (and [[data processing|information processing]] performance improvements thanks to [[Moore's law]]) made it possible to securely encrypt voice and [[video call]]s, teleprinters were long used in combination with electromechanical or electronic [[cryptographic]] devices to provide secure [[communication channel]]s. Being limited to text only was an acceptable trade-off for security.