Telephone: Difference between revisions

The telephone is a telecommunications device designed to transmit speech by means of electric signals. Generally attributed to the inventor Alexander Graham Bell, the first was built in Boston, Massachusetts, in 1876. According to other Sources Philip Reis invented it in 1860, but due to a false translation of the german word "Telephon" his invention was considered only the predecessor of Bell's one.

On June 15th, 2002, the US Congress officially recognized Antonio Meucci as the inventor of the telephone.

The history of additional inventions and improvements includes the carbon microphone (later replaced by the electret microphone now used in almost all telephone transmitters), the manual switchboard, the rotary dial, the automatic telephone exchange, the computerized telephone switch, Touch Tone(R) dialing (DTMF), the digitization of sound using different coding techniques including pulse code modulation or PCM (which is commonly used for .WAV files and on compact disks). Newer systems include ISDN, DSL, cell phone (mobile) systems, digital cell phone systems, and the third generation cell phone systems that promise to allow high-speed packet data transfer.

The industry was early on divided into telephone equipment manufacturers and telephone network operators (telcos), the latter often holding a national monopoly. In the United States, the Bell System was vertically integrated: it fully or partially owned the telephone companies that provided service to about 80% of the telephones in the country and also owned Western Electric, which manufactured or purchased virtually all the equipment and supplies used by the local telephone companies. The Bell System divested itself of the local telephone companies in 1984 in order to settle an antitrust suit brought against it by the United States Department of Justice.

The first transatlantic telephone call was between New York City and London and occurred on January 7, 1927.

Telephone Equipment Manufacturers

Ericsson, Lucent, Marconi, Motorola, Nokia, Nortel, Siemens,

Telephone Equipment Research Labs

Bell Labs

Telephone Operating Companies

Some Telco names (in alphabetic order) include: AT&T, BC TEL, Bell, Bell Canada, British Telecom, Cable and Wireless, Deutsche Telekom, GTE, ITT, NTL, NTT, Telefonica, Teleglobe, Telewest, Telstra, Telia, TELUS, Verizon

Land-line based phone systems

The network that connects most phones together is known as the PSTN (public switched telephone network). Phone lines are usually copper wires which form a circuit between the subscriber and the exchange, although some recent installations may use optical fibre for part of the distance. An analog line typically uses frequencies of 0-3.5 kHz, with frequencies higher than this filtered at the exchange. The analog speech signals are carried over the digital backbone network as a stream of digitally encoded samples at a sample rate of 8 kHz. The frequences above 4 kHz can be utilised for DSL connections.

Automatic telephone systems generally use numeric addresses, more commonly known as telephone numbers. The addressing system often distinguishes local, long-distance and international calls. Local calls are initiated by dialling the local number. A long-distance number is indicated by a long-distance prefix (CCITT recommends "0") followed by area code and a number local to that area. International phone calls require an international prefix (CCITT recommends "00") followed by area code and local number. US and Canadian phone systems use "1" as the long distance prefix and "011" for international prefix. See country calling codes for access codes to international telephone services.

Larger companies and organizations often employ a PABX (Private Automatic Branch Exchange). This is a telephone switch that defines its own local phone number range, which is commonly embedded in a public local phone number range. Some of the largest companies now even have their own internal telephone networks across the country, or even throughout the world, with limited gateways into the PSTN.

Most PSTN systems use analog signalling between individual phones and the local switch. If digital signalling is used for an individual phone, the system used is usually ISDN (Integrated Services Digital Network).

Between switches in the PSTN, most signalling is now digital using Signalling System 7 ("SS7").

Wireless phone systems

Most wireless phone systems are cell-structured. Wireless communication is used between the handsets and the cell. Communication between cells can be wireless, or over ground cables. When an active handset moves from one cell to another, the call is automatically transferred to the next cell without interrupting the call.

There are now multiple standards for common carrier wireless telephony, often with multiple incompatable standards used in the same nation:

• Analog first generation
  • marine and mobile radio telephony
  • AMPS
    • CDPD data service on AMPS
  • NMTS
• Digital second generation (2G)
  • CDMA IS-95A
  • GSM
    • (different frequencies for different continents: see GSM article)
  • iDEN
  • TDMA IS-136
• Digital 2.5G
  • CDMA IS-95B
  • GSM GPRS
  • i-Mode
• Digital 3G
  • CDMA 2000
  • GSM EDGE
  • W-CDMA

See also

ADSL, AIOD leads, [ANAC] Assistive Technology, Automatic redial, Basic exchange telecommunications radio service, Bomb threat, Call center, Call originator, Caller, Caller ID, Camp-on busy signal, Computer telephony integration (CTI), Crank call, Customer premises equipment, Deaf, Dial Tone, Digital subscriber line, Direct distance dialing, Dual tone multi frequency, Emergency telephone number, End instrument, Fax Foreign exchange service, Help desk, Infrastructure, Interactive voice response (IVR), Line, Local loop Long-distance operator, Party line, Modem Payphone, Plain Old Telephone Service (POTS), Phone Phone phreaking, Photophone, Phreaking, Post office Prank call, Private line, Ringer equivalency number, Ringing signal, Rural radio service, Smartphone, TAPI, Telecommunications Device for the Deaf (TDD or TTY) Telephone area code Telephone directory, Telephone exchange Telephone tapping Telegraph, Telemarketing, Videotex Voice over Internet Protocol, War dialing, Wide Area Telephone Service, Wireless network, Wi-Fi 610 (telephone), 431A

US Specific

Federal Standard 1037C-Glossary of telephony terms, Federal Regulations - Part 68, Modification of Final Judgment, Local access and transport area (LATA), Telecommunication