Editing Telephone (section)

==Early commercial instruments==
Early telephones were technically diverse. Some used a [[water microphone]], some had a metal diaphragm that induced current in an electromagnet wound around a permanent magnet, and some were [[Dynamic microphone|dynamic]] – their diaphragm vibrated a coil of wire in the field of a permanent magnet or the coil vibrated the diaphragm. The sound-powered dynamic variants survived in small numbers through the 20th century in military and maritime applications, where its ability to create its own electrical power was crucial. Most, however, used the Edison/Berliner [[carbon transmitter]], which was much louder than the other kinds, even though it required an [[induction coil]] which was an [[impedance matching]] transformer to make it compatible with the impedance of the line. The Edison patents kept the Bell monopoly viable into the 20th century, by which time the network was more important than the instrument.

Early telephones were locally powered, using either a dynamic transmitter or by the powering of a transmitter with a local battery. One of the jobs of [[outside plant]] personnel was to visit each telephone periodically to inspect the battery. During the 20th century, telephones powered from the telephone exchange over the same wires that carried the voice signals became common.

Early telephones used a single wire for the subscriber's line, with [[Single wire earth return|ground return]] used to complete the circuit (as used in [[telegraph]]s). The earliest dynamic telephones also had only one port opening for sound, with the user alternately listening and speaking (or rather, shouting) into the same hole. Sometimes the instruments were operated in pairs at each end, making conversation more convenient but also more expensive.

At first, the benefits of a telephone exchange were not exploited. Instead, telephones were leased in pairs to a [[subscriber]], who had to arrange for a telegraph contractor to construct a line between them, for example, between a home and a shop. Users who wanted the ability to speak to several different locations would need to obtain and set up three or four pairs of telephones. [[Western Union]], already using telegraph exchanges, quickly extended the principle to its telephones in [[New York City]] and [[San Francisco]], and Bell was not slow in appreciating the potential.

[[Signaling (telecommunications)|Signalling]] began in an appropriately primitive manner. The user alerted the other end, or the exchange [[Switchboard operator|operator]], by [[whistling]] into the transmitter. Exchange operation soon resulted in telephones being equipped with a bell in a [[ringer box]], first operated over a second wire, and later over the same wire, but with a condenser ([[capacitor]]) in series with the bell coil to allow the [[Alternating current|AC]] ringer signal through while still blocking [[Direct current|DC]] (keeping the phone "[[on hook]]"). Telephones connected to the earliest [[Strowger switch]] automatic exchanges had seven wires, one for the [[Changeover switch|knife switch]], one for each [[telegraph key]], one for the bell, one for the [[push-button]] and two for speaking. Large wall telephones in the early 20th century usually incorporated the bell, and separate [[bell box]]es for desk phones dwindled away in the middle of the century.

Rural and other telephones that were not on a common battery exchange had a [[telephone magneto|magneto]] hand-cranked generator to produce a high voltage alternating signal to ring the bells of other telephones on the line and to alert the operator. Some local farming communities that were not connected to the main networks set up [[barbed wire telephone lines]] that exploited the existing system of field fences to transmit the signal.

In the 1890s a new smaller style of telephone was introduced, packaged in three parts. The transmitter stood on a stand, known as a "[[Candlestick telephone|candlestick]]" for its shape. When not in use, the receiver hung on a hook with a switch in it, known as a "switchhook". Previous telephones required the user to operate a separate switch to connect either the voice or the bell. With the new kind, the user was less likely to leave the phone "off the hook". In phones connected to magneto exchanges, the bell, induction coil, battery and magneto were in a separate bell box or "[[ringer box]]".<ref>{{cite web
 |url=http://www.telephonymuseum.com/ringer_boxes.htm
 |archive-url=https://web.archive.org/web/20011012231415/http://www.telephonymuseum.com/ringer_boxes.htm
 |url-status=usurped
 |archive-date=2001-10-12
 |title=Ringer Boxes
 |publisher=Telephonymuseum.com
 |access-date=2010-05-23
}}</ref> In phones connected to common battery exchanges, the ringer box was installed under a desk, or other out-of-the-way place, since it did not need a battery or magneto.

Cradle designs were also used at this time, having a handle with the receiver and transmitter attached, now called a [[handset]], separate from the cradle base that housed the magneto crank and other parts. They were larger than the "candlestick" and more popular.

Disadvantages of single-wire operation such as crosstalk and [[Mains hum|hum from nearby AC power wires]] had already led to the use of twisted pairs and, for long-distance telephones, [[four-wire circuit]]s. Users at the beginning of the 20th century did not place [[long-distance call]]s from their own telephones but made an appointment and were connected with the assistance of a telephone operator.<ref>{{Cite web |last=DiPirro |first=Peggy |title=The beginning of long distance telephone service |url=https://www.palmbeachpost.com/story/news/2018/03/12/the-beginning-long-distance-telephone/7121125007/ |access-date=2022-08-25 |website=The Palm Beach Post |language=en-US |archive-date=2023-03-06 |archive-url=https://web.archive.org/web/20230306065058/https://www.palmbeachpost.com/story/news/2018/03/12/the-beginning-long-distance-telephone/7121125007/ |url-status=live }}</ref>

What turned out to be the most popular and longest-lasting physical style of telephone was introduced in the early 20th century, including Bell's [[Model 202 telephone|202-type]] desk set. A carbon granule transmitter and electromagnetic receiver were united in a single molded plastic handle, which when not in use was secured in a cradle in the base unit. The circuit diagram of the model 202 shows the direct connection of the transmitter to the line, while the receiver was inductively coupled. In local battery configurations, when the local loop was too long to provide sufficient current from the exchange, the transmitter was powered by a local battery and inductively coupled, while the receiver was included in the local loop.<ref>{{usurped|1=[https://web.archive.org/web/20070616083345/http://www.porticus.org/bell/images/we-102.jpg Circuit Diagram, Model 102]}}, Porticus Telephone website.</ref> The coupling transformer and the ringer were mounted in a separate enclosure, called the subscriber set. The dial switch in the base interrupted the line current by repeatedly but very briefly disconnecting the line one to ten times for each digit, and the hook switch (in the center of the circuit diagram) disconnected the line and the transmitter battery while the handset was on the cradle.

In the 1930s, telephone sets were developed that combined the bell and induction coil with the desk set, obviating a separate ringer box. The [[rotary dial]] becoming commonplace in the 1930s in many areas enabled customer-dialed service, but some magneto systems remained even into the 1960s.  The village of [[Bryant Pond, Maine]] is believed to be the last telephone exchange in the U.S. to convert from magneto to direct-dial service on October 11, 1983.<ref>{{Cite web|url=https://www.upi.com/Archives/1983/10/10/End-of-an-era-for-Maine-crank-phones/4303434606400/|title=End of an era for Maine crank phones|website=www.upi.com/Archives/1983/10/10/End-of-an-era-for-Maine-crank-phones/4303434606400/|access-date=March 9, 2025}}</ref> After World War II, the telephone networks saw rapid expansion and more efficient telephone sets, such as the [[model 500 telephone]] in the United States, were developed that permitted larger local networks centered around central offices. A breakthrough new technology was the introduction of Touch-Tone signaling using [[push-button telephone]]s by [[American Telephone & Telegraph Company]] (AT&T) in 1963.<ref>{{Cite web |title=Tone dialing telephones are introduced, November 18, 1963 |url=https://www.edn.com/tone-dialing-telephones-are-introduced-november-18-1963/ |website=EDN |date=18 November 2019 |access-date=25 August 2022 |archive-date=7 November 2022 |archive-url=https://web.archive.org/web/20221107053607/https://www.edn.com/tone-dialing-telephones-are-introduced-november-18-1963/ |url-status=live }}</ref>

<gallery widths="200px" heights="200px">
File:Ericsson bakelittelefon 1931 sv.jpg|[[Ericsson DBH 1001 telephone|Ericsson DBH 1001]] (ca. 1931), the first combined telephone made with a Bakelite housing and handset.
File:Minalinpampangajf2520 02.JPG|Telephone used by American soldiers (WWII, [[Minalin, Pampanga]], [[Philippines]])
File:Oldphone.ogv|Video shows the operation of an [[Ericofon]]
File:Motorola L71 on the China Mobile network 20100521.jpg|One type of [[mobile phone]], called a cell phone
</gallery>