Phone Call Recorder

private branch exchange

Originally an organization's manual switchboard (operated by a person plugging cables into sockets) was known as a PMBX (Private Manual Branch eXchange). These were gradually replaced by automated electromechanical and then electronic switching systems, called PABXs (Private Automatic Branch eXchange). As PMBXes are almost unheard of, the terms PABX and PBX have become synonymous. Using a PBX saves connecting all of a business's telephone sets separately to the public telephone network (PSTN or ISDN). Such a set-up would require every set to have its own line (usually with a monthly recurring line charge), and "internal" calls would have to be routed out of the building to a central switch, only to come back in again. In addition to telephone sets, fax machines, modems and many other communication devices can be connected to a PBX as well (although the PBX may degrade line quality for modems). For this reason, all such devices are generally referred to as extensions. The PBX equipment is typically installed at a business's premises, and connects calls between the telephones installed there. In addition, a limited number of outside lines (called trunk lines) are usually available for making and receiving calls external to the site (i.e. to the public telephone network). Companies with multiple sites can connect their PBXs together with trunk lines. PBX-like services can also be provided by equipment located off site at a central provider, delivering services over the public telephone network. This is known as a hosted PBX. For example, most local phone companies offer a Centrex service in which each extension has a trunk line connected to the telephone company's Central Office. Other companies offer similar services. PBXs are distinguished from smaller "key systems" by the fact that external lines are not normally indicated or selectable at an individual extension. From a user's point of view calls on a key system are made by selecting a specific outgoing line and dialing the external number; calls on a PBX are made by dialing 9 (or 0 in some systems) followed by the external number; an outgoing trunk line is automatically selected upon which to complete the call. One of the latest trends in PBX development is the VoIP PBX, also known as an IPBX, which uses the Internet Protocol to carry calls. Most modern PBXs support VoIP. ISDN PBX systems also replaced some traditional PBXs in the 1990s, as ISDN offers features such as conference calling, call forwarding, programmable caller ID, etc. Historically, the expense of PBX systems has put them out of reach of small businesses and individuals. However, recent open source projects combined with cheap modern hardware are sharply reducing the cost of PBX ownership. Functionally, the PBX performs three main duties: Establishing connections (circuits) between the telephone sets of two users. (e.g. mapping a dialed number to a physical phone, ensuring the phone isn't already busy) Maintaining such connections as long as the users require them. (i.e. channeling voice signals between the users) Providing information for accounting purposes (e.g. metering calls) In addition to these basic functions, PBXs offer many other capabilities, with different manufacturers providing different features in an effort to differentiate their products. Here is a short list of common capabilities (note that each manufacturer may have a different name for each capability): Call transfer; dialing.modem">Direct Inward Dialing; Customised Abbreviated dialing (Speed Dialing); Voice mail; Follow-me; Call forwarding on absence; Call forwarding on busy; Music on hold; Automatic ring back; Night service; Call distribution (ACD, fixed sequences, ...); Call waiting; Call pick-up; Call park; Call conferencing; Custom greetings; Shared message boxes (where a department can have a shared voicemail box); Automated directory services (where callers can be routed to a given employee by keying or speaking the letters of the employee's name); Call accounting. Interfaces for connecting extensions to a PBX include: POTS (Plain Old Telephone System) - the common two-wire interface used in most homes. This is cheap and effective, and allows almost any standard phone to be used as an extension. proprietary - the manufacturer has defined a protocol. One can only connect the manufacturer's sets to their PBX, but the benefit is more visible information displayed and/or specific function buttons. DECT - a standard for connecting cordless phones. Internet Protocol - For example, H.323 and SIP. Interfaces for connecting PBXs to each other include: proprietary protocols - if equipment from several manufacturers are on site, the use of a standard protocol is required. QSIG - for connecting PBXs to each other, usually runs over T1 (T-carrier) or E1 (E-carrier) physical circuits. DPNSS - for connecting PBXs to trunk lines. Standardised by British Telecom, this usually runs over E1 (E-carrier) physical circuits. Internet Protocol - H.323, SIP and IAX protocols are IP based solutions which can handle voice and multimedia (e.g. video) calls. Interfaces for connecting PBXs to trunk lines include: standard POTS (Plain Old Telephone System) lines - the common two-wire interface used in most domestic homes. This is adequate only for smaller systems, and can suffer from not being able to detect incoming calls when trying to make an outbound call. ISDN - the most common digital standard for fixed telephony devices. This can be supplied in either Basic (2 circuit capacity) or Primary (24 or 30 circuit capacity) versions. Most medium to large companies would use Primary ISDN circuits carried on T1 or E1 physical connections. Internet Protocol - H.323, SIP, MGCP, and IAX protocols operate over IP and are supported by some network providers. Interfaces for collecting data from the PBX: Serial interface - historically used to print every call record to a serial printer. Now an application connects via serial cable to this port. Network Port (Listen mode) - where an external application connects to the TCP or UDP port. The PBX the starts streaming information down to the application. Network Port (Server mode) - The PBX connects to another application or buffer. File - The PBX generates a file containing the call records from the PBX. The call records from the PBX are called SMDR, CDR, or CIL.

List of telephony terms:

3gpp - a-law - abbreviated dialing - adsl - ani - answering machine - apn - automatic ring back - b-channel - baud - bell 202 modem - bit rate - bonding - bri - busy signal - cable modem - call-progress tones - call accounting - call capture - call forwarding - call originator - call park - call pick-up - call transfer - call waiting - call waiting deluxe - called party - caller id - caller id spoofing - calling party - carrier wave - cbr - ccitt - cdma - cdma2000 - cellular repeater - celp - channel - clec - clock rate - codec - collect call - conference - conference call - crc - csd - d-channel - data compression - device driver - dial-up - dial - dial tone - direct-inward-dialing - direct distance dialing - distinctive ring - dnis - dsl - dsp - dtmf - dtr - duplex - echo cancellation - edge - extension - fax - fcc - fdma - fidonet - follow-me - g.711 - g.723.1 - g.723 - g.726 - g.lite - gprs - gps - gsm - h.323 - harmonic - headphones - hscsd - hspda - iad - idsn - internet call waiting - isp - ivr - jack plug - local loop - long distance - microcontroller - mobile phone - modem - modulation - mu-law - music-on-hold - night service - off-hook - on-hook - pabx - pager - payphone - pbx - pcm - pots - prank call - precise tone plan - pstn - pulse dialling - push to talk - ring modulation - ring tone - ringback - ringing signal - rj11 - roaming - serial communications - serial port - signal noise - sim - simplex - sit - sms - softmodem - switchboard operator - tapi - tdma - telecommunications - telemarketing - telephone - telephone call - telephone card - telephone company - telephone exchange - telephone line - telephone number - telephone numbering plan - telephone operator - telephone switchboard - telephony - tts - twisted pair - umts - v.32 - v.32bis - v.34 - v.42bis - vbr - vertical service code - voicemail - voip - vox - wap - wav - wi-fi - wimax - wire