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67-475: PHS is essentially a cordless telephone like DECT , with the capability to handover from one cell to another. PHS cells are small, with transmission power of base station a maximum of 500 mW and range typically measures in tens or at most hundreds of metres (some can range up to about 2 kilometres in line-of-sight), contrary to the multi-kilometre ranges of CDMA and GSM . This makes PHS suitable for dense urban areas, but impractical for rural areas, and

134-410: A base station connected to the public telephone network . The operational range is limited, usually to the same building or within some short distance from the base station. A cordless telephone differs functionally from a mobile telephone in its limited range and by depending on the base station on the subscriber premises. Current cordless telephone standards, such as PHS and DECT , have blurred

201-406: A timeslot because DS0s are aggregated in time-division multiplexing (TDM) equipment to form higher capacity communication links. A Digital Signal 1 (DS1) circuit carries 24 DS0s on a North American or Japanese T-carrier (T1) line, or 32 DS0s (30 for calls plus two for framing and signaling) on an E-carrier (E1) line used in most other countries. In modern networks, the multiplexing function

268-403: A wireless access point or base station that supports the same technology. Also required is a call management function and a gateway to the public switched telephone network (PSTN). This may or may not be integrated in the base-station. A Voice over IP service can be used by phones that use wireless data access points, thus using a broadband Internet connection to defer the connection to

335-582: A PHS-based telephony service in Betim , state of Minas Gerais, and Transit Telecom announced a rollout of a PHS network in 2007. China Telecom operated a PAS system in China, although technically it was not regarded as allowed to provide mobile services, because of some particularities of the Chinese governance. China Netcom , the other fixed-line operator in China, also provides Xiaolingtong service. The system

402-641: A basic form of scrambling to help limit unauthorized eavesdropping . These phones share the 49.8 MHz band (49.830 - 49.890) with some wireless baby monitors . 900 MHz cordless phones are rarely sold but have a huge installed base. Features include even shorter antennas, up to 30 auto selecting channels, and higher resistance to interference. Available in several varieties; analog, analog spread spectrum (100 kHz bandwidth), digital, and digital spread spectrum, most being sold today are low-cost analog models, which are still susceptible to eavesdropping. Digital variants can still be scanned, but are received as

469-653: A benchmark for the development of the Telecommunications Industry Association 's TIA-TSB-116 standard on voice-quality recommendations for IP telephony, to determine acceptable levels of audio latency and echo. In most countries, the government has a regulatory agency dedicated to provisioning of PSTN services. The agency regulate technical standards, legal requirements, and set service tasks may be for example to ensure that end customers are not over-charged for services where monopolies may exist. These regulatory agencies may also regulate

536-461: A couple of city blocks. These models became obsolete because they are susceptible to eavesdropping, and interference from fluorescent lighting and automobile ignition systems. However, under ideal conditions they could have 0.5 miles (0.80 km) or more range. 43–50 MHz cordless phones had a large installed base by the early 1990s, and featured shorter flexible antennas and automatic channel selection. Due to their popularity, an overcrowding of

603-444: A digital hiss and therefore are difficult to eavesdrop upon. Digital transmission is immune to static interference but can experience signal fade (brief silence) as the phone goes out of range of the base. Newer Digital Spread Spectrum (DSS) variants spread their signal over a range of frequencies, providing more resistance to signal fade. This technology enabled the digital information to spread in pieces among several frequencies between

670-523: A duplex voice communication link including controls provided between a base station connected directly to a telephone line of a telephone exchange and a mobile unit consisting of a small, compact cordless telephone instrument containing transmitter, receiver and control circuits powered by a rechargeable battery pack. A single logic tone is transmitted and detected for all logical control for ring signals, on-hook and off-hook signals and dial pulses. Cordless phones became widely used in home and workplaces during

737-401: A host of other devices, including baby monitor , microwave oven , Bluetooth , and wireless LAN ; thus, it is likely that a cordless phone will suffer interference from signals broadcast by those devices, and also may itself generate interference. It is also possible for a cordless phone to interfere with the 802.11a wireless standard, as the 802.11a standard can be configured to operate in

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804-569: A network of fixed-line analog telephone systems, the PSTN is almost entirely digital in its core network and includes mobile and wireless networks, all of which are currently transitioning to use the Internet Protocol to carry their PSTN traffic. The technical operation of the PSTN adheres to the standards internationally promulgated by the ITU-T . These standards have their origins in

871-501: A quality that is just adequate for the parties to understand each other. Typical bandwidth is 3.6 kHz; only a fraction of the frequencies that humans can hear, but enough to make the voice intelligible. No phone handset can improve on this quality, as it is a limitation of the phone system itself. Higher-quality phones can transfer this signal to the handset with less interference over a greater range, however. Most cordless telephones, no matter what frequency band or transmission method

938-400: Is accelerated by combining lines, each of which basically is 32 kbit/s. The first version of AIR-EDGE, introduced in 2001, provided 32 kbit/s service. In 2002, 128 kbit/s service (AIR-EDGE 4×) started and in 2005, 256 kbit/s (8×) service started. In 2006, the speed of each line was also upgraded to 1.6 times with the introduction of "W-OAM" technology. The speed of AIR-EDGE 8×

1005-840: Is also a popular option for providing a wireless local loop , where it is used for bridging the " last mile " gap between the POTS network and the subscriber's home. It was developed under the concept of providing a wireless front-end of an ISDN network. Thus a PHS base station is compatible with ISDN and is often connected directly to ISDN telephone exchange equipment e.g. a digital switch. In spite of its low-cost base station , micro-cellular system and "Dynamic Cell Assignment" system, PHS offers higher number-of-digits frequency use efficiency with lower cost (throughput per area basis), compared with typical 3G cellular telephone systems. It enables flat-rate wireless service such as AIR-EDGE , throughout Japan. The speed of an AIR-EDGE data connection

1072-436: Is illegal in many countries). Though many such analog models are still produced, modern digital technology is available to reduce the risk of eavesdropping . Digital Spread Spectrum (DSS) typically uses frequency hopping to spread the audio signal (with a 3 kHz bandwidth) over a much wider range of frequencies in a pseudorandom way. Spreading the signal out over a wider bandwidth is a form of redundancy , and increases

1139-488: Is moved as close to the end user as possible, usually into cabinets at the roadside in residential areas, or into large business premises. These aggregated circuits are conveyed from the initial multiplexer to the exchange over a set of equipment collectively known as the access network . The access network and inter-exchange transport use synchronous optical transmission, for example, SONET and Synchronous Digital Hierarchy (SDH) technologies, although some parts still use

1206-399: Is no specific requirement for any particular transmission mode on the older bands, but in practice many legacy phones also have digital features such as DSSS and FHSS . Some cordless phones formerly advertised as 5.8 GHz actually transmit from base to phone on 5.8 GHz and transmit from phone to base on 2.4 GHz or 900 MHz, to conserve battery life. The 1.9 GHz band

1273-659: Is returned to the cradle. Additionally, the digital nature of the signal increases its tolerance to noise, and some systems even encrypt the digital signal for additional security. Roaming cordless phone handsets exist which are not tethered to any particular base station, but which also do not use traditional mobile (cellular) phone networks. These most commonly use digital technologies like DECT , 2.4 GHz unlicensed spectrum, or 802.11a /b/g standards-based wireless LAN technology. Analog equivalents do exist and can provide longer reach, but with potential loss of confidentiality and voice quality. The cordless phone handset connects to

1340-399: Is switched using a call set up protocol (usually ISUP ) between the telephone exchanges under an overall routing strategy . The call is carried over the PSTN using a 64 kbit/s channel, originally designed by Bell Labs . The name given to this channel is Digital Signal 0 (DS0). The DS0 circuit is the basic granularity of circuit switching in a telephone exchange. A DS0 is also known as

1407-552: Is the aggregate of the world's telephone networks that are operated by national, regional, or local telephony operators. It provides infrastructure and services for public telephony . The PSTN consists of telephone lines , fiber-optic cables , microwave transmission links, cellular networks , communications satellites , and undersea telephone cables interconnected by switching centers , such as central offices , network tandems , and international gateways, which allow telephone users to communicate with each other. Originally

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1474-416: Is up to 402 kbit/s with the latest "W-OAM" capable instrument. In April 2007, "W-OAM typeG" was introduced allowing data speeds of 512 kbit/s for AIR-EDGE 8x users. Furthermore, the "W-OAM typeG" 8× service was planned to be upgraded to a maximum throughput of 800 kbit/s, when the upgrading for access points (mainly switching lines from ISDN to fibre optic ) in its system are completed. Thus it

1541-609: Is used by the DECT 6.0 phone standard and is considered more secure than the other shared frequencies. The vast majority of new cordless phone devices sold in North America, whether connected by landline or to mobile phones (usually via Bluetooth ), now use DECT 6.0. However, DECT 6.0's late start compared to DECT elsewhere has led to a large installed base of legacy cordless phones using other frequencies, many of which remain in use today despite increasingly common interference with

1608-502: Is used, will hardly ever exactly match the sound quality of a high-quality wired telephone attached to a good telephone line . This limitation is caused by a number of issues, including the following: Most manufacturers claim a range of about 30 metres (98 ft) for their 2.4 GHz and 5.8 GHz systems, but inexpensive models often fall short of this claim. However, the higher frequency often brings advantages. The 900 MHz and 2.4 GHz band are increasingly being used for

1675-622: The Broadband Integrated Services Digital Network (B-ISDN). The B-ISDN vision was overtaken by the disruptive technology of the Internet . At the turn of the 21st century, the oldest parts of the telephone network still used analog baseband technology to deliver audio-frequency connectivity over the last mile to the end-user. However, digital technologies such as DSL , ISDN , FTTx , and cable modems were progressively deployed in this portion of

1742-618: The Federal Communications Commission for uses that include cordless phones. These are: Over-crowding of earlier frequency allocations led users to discontinue using telephone equipment that operated on those frequencies, leaving those bands relatively clear. Radio hobbyists monitor usage of the older equipment with telephone activity in the US AM broadcast band, some 27 MHz frequencies and most older 43-50 MHz frequencies. 1.7 MHz cordless phones were

1809-498: The PSTN to a remote gateway operated by the service provider. Unlike wired telephones that are powered from the telephone company's central station batteries, a cordless phone base station required electrical power to operate. During a power interruption, the cordless base station will not be operable, while wired sets may continue to operate. Public switched telephone network The public switched telephone network ( PSTN )

1876-421: The last mile from the exchange to the telephone in the home (also called the local loop ). To carry a typical phone call from a calling party to a called party , the analog audio signal is digitized at an 8 kHz sample rate with 8-bit resolution using a special type of nonlinear pulse-code modulation known as G.711 . The call is then transmitted from one end to another via telephone exchanges. The call

1943-409: The signal-to-noise ratio , yielding longer range and less susceptibility to interference. Higher frequency bands provide more room for these wide-bandwidth signals. To an analog receiver like a scanner, a DSS signal sounds like bursts of noise. Only the base unit using a matching pseudorandom number can decode the signal, and it chooses from one of thousands of such unique codes each time the handset

2010-485: The 1970s, the telecommunications industry began implementing packet-switched network data services using the X.25 protocol transported over much of the end-to-end equipment as was already in use in the PSTN. These became known as public data networks , or public switched data networks. In the 1980s, the industry began planning for digital services assuming they would follow much the same pattern as voice services and conceived end-to-end circuit-switched services, known as

2077-566: The 21st century are digital. Digital technology has helped provide clear sound and limit casual eavesdropping. Many cordless phones have one main base station and can add up to three or four additional bases. This allows for multiple voice channels that allow three-way conference calls between the bases. This technology also allows multiple handsets to be used at the same time, and up to two handsets can have separate conversations with outside parties. Manufacturers usually advertise that their higher frequency systems improve audio quality and range. In

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2144-495: The 5.8 GHz range. However, this can easily be fixed by reconfiguring the wireless LAN device to work in the 5.180 GHz to 5.320 GHz band. The newer 1.9 GHz band is reserved for use by phones that use the DECT standard, which should avoid interference issues in the unlicensed 900 MHz, 2.4 GHz, and 5.8 GHz bands. Many analog phone signals are easily picked up by radio scanners , allowing anyone within range to listen in on conversations (though this

2211-519: The PHS system with Intelligent Network and marketed the service as Personal Communication Telephone (PCT). The integrated system was the world's first that allowed the fixed line telephone subscribers of the public switched telephone network to use PHS as a value added service with the same telephone number and shared the same voice mailbox. The PCT service was commercially launched in November 1999 with

2278-504: The PSTN evolved over time to support an increasing number of subscribers, call volume, destinations, features, and technologies. The principles developed in North America and in Europe were adopted by other nations, with adaptations for local markets. A key concept was that the telephone exchanges are arranged into hierarchies, so that if a call cannot be handled in a local cluster, it is passed to one higher up for onward routing. This reduced

2345-480: The PSTN, usually for military purposes. There are also private networks run by large companies that are linked to the PSTN only through limited gateways , such as a large private branch exchange (PBX). The task of building the networks and selling services to customers fell to the network operators . The first company to be incorporated to provide PSTN services was the Bell Telephone Company in

2412-715: The United States. In some countries, however, the job of providing telephone networks fell to government as the investment required was very large and the provision of telephone service was increasingly becoming an essential public utility . For example, the General Post Office in the United Kingdom brought together a number of private companies to form a single nationalized company . In more recent decades, these state monopolies were broken up or sold off through privatization . The architecture of

2479-541: The above-mentioned countries. WILLCOM , formerly DDI-Pocket, introduced flat-rate wireless network and flat-rate calling in Japan, which reversed the local fate of PHS up to an extent. In China, there was an explosive expansion of subscribers until around 2005. In Chile, Telefónica del Sur launched a PHS-based telephony service in some cities of the southern part of the country in March 2006. In Brazil, Suporte Tecnologia has

2546-408: The band led to an allocation of additional frequencies; thus manufacturers were able to sell models with 25 channels instead of just 10 channels. Although less susceptible to interference than previous AM units, these models are no longer in production and are considered obsolete because their frequencies are easily heard on practically any radio scanner. Advanced models began to use voice inversion as

2613-401: The base station). The cordless handset contains a rechargeable battery , which the base station re-charges when the handset rests in its cradle. Radio telephony (telephony without wires) predated cordless phones by at least two decades. The first, MTS, or Mobile Telephone Service went into service in 1946. Because the range was intended to cover the widest possible service area, capacity

2680-472: The development of local telephone networks, primarily in the Bell System in the United States and in the networks of European ITU members. The E.164 standard provides a single global address space in the form of telephone numbers . The combination of the interconnected networks and a global telephone numbering plan allows telephones around the world to connect with each other. Commercialization of

2747-520: The direction of W.D. Goodale, Jr. By 1964, breadboard models were working in the lab. During 1964-65 these were refined and packaged to test around the Bell Labs Holmdel N.J. facilities. The system operated under an experimental license on crystal controlled channels in the 35 and 43 MHz bands using FM, a low power transmitter and a sensitive superhet receiver. Full supervision of all telephone functions, including on-off hook and dialing

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2814-484: The earliest models available at retailers, and are generally identifiable by their large metal telescoping antennas. Channels just above the AM broadcast band were selected manually by the user. Some of the frequencies used are now part of the expanded AM radio band, and can be heard by anyone with an AM radio. There are reports of people still using these phones, and using them as makeshift AM radio stations that can be heard for

2881-622: The early 1980s. According to The New York Times , the number of cordless phones sold in the United States grew from 50,000 in 1980 to 1 million in 1982. They quickly became popular because of their convenience and portability, despite fears that their reliance on radio signals would make them vulnerable to eavesdropping or other malfeasance. In 1994, digital cordless phones in the 900 MHz frequency range became available to consumers. These new types of phones provided better audio quality because it could filter out interference and its signals could penetrate walls more easily. Digital signals allowed

2948-399: The end of the 20th century. The growth of the PSTN was enabled by teletraffic engineering techniques to deliver quality of service (QoS) in the network. The work of A. K. Erlang established the mathematical foundations of methods required to determine the capacity requirements and configuration of equipment and the number of personnel required to deliver a specific level of service. In

3015-426: The ever growing use of Wi-Fi , Bluetooth and other unlicensed digital radio standards, especially at 2.4 GHz and 5.8 GHz. In Europe, the 1.9 GHz (1880–1900 MHz) band was set aside for the DECT phone standard from its inception. DECT, on its European band & related frequencies, has largely displaced all other cordless phone standards worldwide except for North America. Many cordless phones in

3082-412: The exchange principle already employed in telegraph networks. Each telephone was wired to a telephone exchange established for a town or area. For communication outside this exchange area, trunks were installed between exchanges. Networks were designed in a hierarchical manner until they spanned cities, states, and international distances. Automation introduced pulse dialing between the telephone and

3149-521: The exchange so that each subscriber could directly dial another subscriber connected to the same exchange, but long-distance calling across multiple exchanges required manual switching by operators. Later, more sophisticated address signaling, including multi-frequency signaling methods, enabled direct-dialed long-distance calls by subscribers, culminating in the Signalling System 7 (SS7) network that controlled calls between most exchanges by

3216-437: The ideal case, higher frequencies actually have worse signal propagation as shown by the basic Friis transmission equation , and path loss tends to increase at higher frequencies as well. Practical influences on quality and range are signal strength , antenna quality, the method of modulation used, and interference, which varies locally. " Plain old telephone service " (POTS) landlines are designed to transfer audio with

3283-505: The network, primarily to provide high-speed Internet access. As of 2023 , operators worldwide are in the process of retiring support for both last-mile analog telephony and ISDN, and transitioning voice service to Voice over IP via Internet access delivered either via DSL , cable modems or fiber-to-the-premises , eliminating the expense and complexity of running two separate technology infrastructures for PSTN and Internet access. Several large private telephone networks are not linked to

3350-415: The number of connecting trunks required between operators over long distances, and also kept local traffic separate. Modern technologies have brought simplifications Most automated telephone exchanges use digital switching rather than mechanical or analog switching. The trunks connecting the exchanges are also digital, called circuits or channels. However analog two-wire circuits are still used to connect

3417-506: The older PDH technology. The access network defines a number of reference points. Most of these are of interest mainly to ISDN but one, the V reference point , is of more general interest. This is the reference point between a primary multiplexer and an exchange. The protocols at this reference point were standardized in ETSI areas as the V5 interface . Voice quality in PSTN networks was used as

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3484-421: The once clear-cut line between cordless and mobile telephones by implementing cell handoff (handover); various advanced features, such as data-transfer; and even, on a limited scale, international roaming . In specialized models, a commercial mobile network operator may maintain base stations and users subscribe to the service. Unlike a corded telephone, a cordless telephone needs mains electricity (to power

3551-470: The peak of 670,000 subscribers in 2001. However, the number of subscribers had declined to 470,000 in 2005 before the breakeven in 2006 after six years of heavy investment up to 15 billion THB. With the popularity of other cellular phone services, the company shifted the focus of the PCT to a niche market segment of youths ages 10-18. Wireless local loop (WLL) systems based on PHS technology are in use in some of

3618-456: The phones to be more secure and decreased eavesdropping; it was relatively easy to eavesdrop on analog cordless phone conversations. In 1995 digital spread spectrum (DSS) was introduced for cordless phones. This technology enabled the spreading of the digital voice transmission over multiple frequencies, improving privacy and reducing interference between different subscribers. In the United States, seven frequency bands have been allocated by

3685-437: The prices charged between the operators to carry each other's traffic . In the United Kingdom, the copper POTS and ISDN-based PSTN is being retired in favour of SIP telephony , with an original completion date of December 2025, although this has now been put back to January 2027. See United Kingdom PSTN switch-off . Voice telephony will continue to follow the E.163 and E.164 standards, as with current mobile telephony, with

3752-500: The receiver and the base, thereby making it almost impossible to eavesdrop on the cordless conversation. The FCC only allows DSS model phones to transmit at the full power of 1 watt, which allows increased range over older analog and digital models. Virtually all new cordless phones sold in the US use DECT 6.0 on the 1.9 GHz band, though legacy phones can remain in use on the older 900 MHz, 2.4 GHz and 5.8 GHz bands. There

3819-425: The service to be ended by the end of 2011. A PHS global roaming service was available between Japan (WILLCOM), Taiwan, and Thailand. This is a list of commercial PHS deployments around the world, all of which are now defunct: PHS-enabled PCMCIA / CompactFlash cards include: Cordless telephone A cordless telephone or portable telephone has a portable telephone handset that connects by radio to

3886-478: The service was pejoratively dubbed as the "poor man's cellular", due to its limited range and roaming abilities. Market share in Japan has been declining and NTT DoCoMo, which has absorbed NTT Personal, and ASTEL terminated the PHS service in January 2008. Most other countries with PHS networks have also terminated offering PHS services and migrated to GSM. In Thailand, TelecomAsia (now True Corporation ) integrated

3953-430: The small cell size also makes it difficult if not impossible to make calls from rapidly moving vehicles. PHS uses TDMA / TDD for its radio channel access method , and 32 kbit/s ADPCM for its voice codec . Modern PHS phone can also support many value-added services such as high speed wireless data / Internet connection (64 kbit/s and higher), WWW access, e-mailing , and text messaging. PHS technology

4020-502: The telephone began shortly after its invention, with instruments operated in pairs for private use between two locations. Users who wanted to communicate with persons at multiple locations had as many telephones as necessary for the purpose. Alerting another user of the desire to establish a telephone call was accomplished by whistling loudly into the transmitter until the other party heard the alert. Bells were soon added to stations for signaling . Later telephone systems took advantage of

4087-573: The telephone, led to the reversal of the Federal Communications Commission ban on direct coupling of consumer equipment to phone lines (known as the landmark Carterfone decision) on June 26, 1968. The original cordless phones, like the Carterfone, were acoustically (not electrically) connected to the public telephone network. In 1977, Douglas G. Talley and L Duane Gregory were granted U.S. patent 4,039,760 for

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4154-458: Was a runaway hit, with over 90 million subscribers signed up as of 2007; the largest equipment vendors were UTStarcom and ZTE . However, low priced mobile phones rapidly replaced PHS. The Ministry of Industry and Information Technology of the People's Republic of China issued notices on 13 February 2009 that both registration of new users and expansion of the network were to be discontinued, with

4221-453: Was an active proponent for directly coupling consumer electronics to the AT&;T -owned telephone lines in the late 1960s. The telephone companies at the time did not permit third-party equipment to be connected to their lines; most telephones were made by Western Electric and leased to the customer by AT&T. The Carterfone coupler, a crude device for interconnecting a two-way radio with

4288-752: Was described in the Bell Laboratories Record, Volume 45 (1967). In 1966, George Sweigert submitted a patent application for a " full duplex wireless communications apparatus". He was awarded U.S. patent 3,449,750 in June 1969. Sweigert, a radio operator in World War II stationed at the South Pacific Islands of Guadalcanal and Bougainville , developed the full duplex concept for untrained personnel, to improve battlefield communications for senior commanders. Sweigert

4355-458: Was expected to exceed the speeds of popular W-CDMA 3G service like NTT DoCoMo 's FOMA in Japan. Developed by NTT Laboratory in Japan in 1989 and far simpler to implement and deploy than competing systems like PDC or GSM , the commercial services were started by three PHS operators (NTT-Personal, DDI-Pocket, and ASTEL) in Japan in 1995, forming the PIAF ( PHS Internet Access Forum ). However,

4422-484: Was extremely low, and the early tube technology made equipment rather large and heavy. The second generation radio telephone, or IMTS, or Improved Mobile Telephone Service became active in 1964. Beginning in 1963, a small team of Bell Laboratories engineers were tasked with developing a practical and fully functional duplex wireless telephone. The team included (in alphabetic order): S.M. Baer, G.C. Balzer, J.M. Brown, W.F. Clemency, M. Rosenthal, and W. Zinsmeister, under

4489-527: Was provided via an out of band tone supervision system. The model developed for home use was designed to look like a standard (although bulky) telephone handset. The base station was a small box connected to a standard telephone network. About 50 units were built in a Western Electric model shop in Andover Mass. for field trials in two Bell System locations in the Boston and Phoenix area. The overall project

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