Business telephone system
A PBX, private branch exchange ( PBX short ) or private branch exchanges (PBX ) is a switching device that connects multiple devices such as phone, fax, answering machine, both with each other and with one or more lines of the public telephone network.
History
In the early telephone systems of the 1930s, the internal and external connections are still made with so-called spacers. Until the late 1970s, telephone exchanges were mechanical in open frame design, then built up in metal cabinets. They consisted mainly of call investigators group voters, voters line, subscriber circuits, official transfers and an attendant. These were replaced in the 1980s by fully digital systems, whose basic function component was a switching network and its input and output lines were switched by a control unit. The family telephone system was a telecommunications solution that was offered in the 1980s by the German Postal Service for private households.
From 2000, came more and more fully IP-based solutions for use, and thus the shift from circuit-switched to pure packet-switched digitized voice data.
The virtual phone system replaced increasingly classical ISDN telephone system in enterprises. Especially small and medium sized companies can benefit from virtual phone systems, because with the help of web-based communication solutions can also be the integration of mobile devices or instant messaging into enterprise communications realized. In addition, virtual phone systems are more flexible than stationary systems and can be extended due to the outsourced server capacity by any number of employees. While the major providers such as Telekom and Vodafone have discovered the business with virtual phone systems late for itself, especially small businesses like Clarity, Placetel, nfon and Sipgate were heavily involved in the market development in Germany.
Functions
The digital system terminal with universal soft keys ( two wire connection) Siemens
The advantages of a telephone system are the free internal calls between connected devices and the better utilization of paid office connections, as not every device must have its own local loop. Other benefits include their own additional features such as call forwarding of telephone calls, toggling, call forwarding or after Timeout. Often there is a so-called query space where a central call is accepted and passed on to the appropriate people.
In addition to automatic switching a telephone system includes a ringing generator, which generates the ringing voltage, and sound generators which generate the signal tones for the caller. The ringing voltage is usually about 60 to 70 volts at 25 hertz.
A telephone system often provides data for the billing of phone calls, plus they usually logged the times and numbers of outgoing and incoming phone calls. They usually also controls which discussions may be conducted by individual extensions from and how extensions are reachable from the outside. Switching between internal and external calls is usually carried out over a one-or multi-digit code, called the access code; In Germany and in other countries this is often the "0". Accessible are the categories:
- "Non- restricted access ": extension must not contain any external calls, in the choice of "0" is equal to Busy.
- " Semi-restricted entitled " extension can be called externally, but may not automatically call to an external number. External calls have to be approved case by case basis by the query space.
- "Site entitled " extension may dial 0, but can cause local calls only.
- " -Restricted ": No restrictions.
Modern systems can assign such rights, much finer still.
Another way to use a telephone system, the pharmacy line.
Technology
The connection of a telephone system to the public telephone network via classical analog telephone lines POTS and / or ISDN, and mobile connections via gateways are now standard.
For the terminals a telephone system has digital and / or analog connection options, known as ports. Devices, depending on the PBX type, wired or wireless ( Mobile Extension) - connected - then mostly based on the DECT standard.
For digital devices ( ISDN telephone, ISDN card, system-specific telephone) is used for connecting an S0 bus ( four wire ) or a system-specific interface as the two-wire interfaces Up0 and UpN.
In general, the terminal and the telephone system are spatially separated and therefore connected via suitable cable installation (for example, telephone cable, twisted-pair cable) or wireless distribution networks (eg DECT) with each other. When connecting via cable distribution mostly come with connection terminals for use or the connection is made via a structured cabling.
Multiple phone systems can be connected together to form a corporate network. The network is implemented as a rule by means of a (also virtual ) leased line. Dial-up lines or microwave are also possible, but are used less frequently. To control the connecting and disconnecting and the transmission of the useful system-specific communication protocols are used in telephone systems from the same manufacturer usually. For cross-linking of telephone systems from different manufacturers, a protocol must be used which are capable of both systems. It usually comes the standardized QSIG protocol ( signaling at the Q reference point ) is used that is supported by almost all manufacturers. Some manufacturers offer but also proprietary protocols to map advanced system-specific functions, such as CorNet from Siemens or ABC -F of Alcatel -Lucent.
In recent years, also phone systems with LAN connection have won both the use of IP telephony system-internal devices as well as for networking several PBX systems over the Internet in popularity.
Technology and Trends
The proliferation of IP-based communication networks enables the convergence of information and telecommunication technology (IT and telecom ). In this connection, telephone systems are increasingly developing more towards pure software-based systems that are based on already standardized or commercially available IT components.
Such solutions are different from classical proprietary solutions, for example, the fact that they are open and interoperable components with respect to such servers, operating systems, protocols and telephone terminals.
Concretely, this means for example that a modern phone system software can be run on standard servers running Linux or Windows server is used as the operating system. Internally, the phone equipment and the trunk connection out such systems then communicate eg via VoIP ( SIP protocol ) so that then standard SIP phones also can be connected. If you want to be connected trunk side by ISDN ( Basic Rate Interface or Primary Rate Interface ) eg and / or connect ISDN and analog telephone terminals, so come corresponding VoIP gateways used.
The benefits to the client company are the fusion of IT and telecommunications system administration, investment protection by the independence of the individual components from each other and frequently also to the increased flexibility of a software-based system.
Difference between the U.S. and Europe
Telephone systems follow in the U.S., the philosophy of several commonly shared lines ( often in U.S. films listen to " The conversation is on line 1 " ) in Europe, however, is the related to the exchange terminal approach in the foreground ( " I associate [ you ] " ).
Miscellaneous
Alternative names
Instead telephone system, other terms are used:
- PBX ( outdated "official" name)
- PBX (also TKAnl or TK -Anl ) ( telecommunication equipment )
- TC system ( Telecommunications System)
- TVA ( private branch exchange )
- PBX (Private Branch Exchange)
- PABX (Private Automatic Branch Exchange)
Alternative, non- hardware-based implementations
Alternative function realizations:
- NetPBX ( internet-based Private Branch Exchange)
- Centrex (a public telephone company provides PBX functions available )
- Asterisk ( Asterisk is a fully realized with open source software PBX )
- Commercial software realized telephone systems ( see list of VoIP software - server software )