Intercom

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Modern door intercom of an intercom with selection of the interlocutor
Intercom with camera

An intercom , also called intercom (from Latin inter between and Latin communicare to communicate), is a means of communication for the transmission of speech by means of electrical signals - similar to the telephone . It is mainly used for internal communication in security-relevant areas. No handset has to be picked up for the speech connection, communication takes place “loudly” like with a hands-free system. That is why the intercom is often used to create an additional, independent conversation level.

Intercom systems, like telephone systems, generally consist of a central device to which several terminals , in this case the intercoms , are connected. But there are also decentralized systems that do not require a central facility.

history

The origin of the intercom lies in Scandinavia . It was originally developed there for office communication, as the post office there also charged fees for internal (internal) telephone calls in the 1930s. The development of the intercom was basically an attempt to create a cheaper internal means of communication.

However, intercom systems were developed earlier for domestic use: In 1899, the Berlin company Paul Haudegen & Co. launched their intercom system that connects three rooms and the kitchen. Under the number 146763 of Telephon-Fabrik Actiengesellschaft , formerly Joseph Berliner "in Hanover , the Imperial Patent Office patented the first" line dialing circuit for loudspeaker ". The first intercom from S. Siedle and Sons followed in 1919. The intercoms from that time were more likely Call systems and not what is understood by this term today.

The first “modern” intercom was brought to the German market in 1935 by AB Gylling . The system was often referred to as the "dog house model" and consisted largely of telephone technology.

With intercom systems, only one participant can speak at a time (who has to switch to his direction), with intercom systems both at the same time (as on the telephone).

The biggest problem with two-way communication is the loss of volume . Until 1951, two-way communication without a loss of volume was not considered possible. Engineers experimented with volume controls using glow paths, attenuation boxes and with the automatic change of speech direction by means of frequency shifting.

Voice-controlled systems are mentioned for the first time in Herbert Petzoldt's 1952 book “Gegen- und Wechselsprechanlagen”. Voice-controlled means here that you cannot listen and speak at the same time (as is the case with the telephone, for example), but only one language direction is activated. The switching of the language direction is controlled by a language balance. This automatically recognizes who is speaking and activates the channel from the speaker to the listener. If both speak at the same time, the louder becomes the speaker and the quieter can only hear.

In this era there were numerous intercom manufacturers who developed the systems in different directions. According to Peter Kerger, these development directions resulted in a breakdown into different industries:

  • Office intercoms
  • Industrial intercoms
  • Hospital communication
  • Home / house intercom technology

The Ericsson group was the first to incorporate electronic call control into a switching center in 1956. This enabled the microphone and loudspeaker of the call station to be accommodated in a common housing for the first time. Shortly afterwards, Philips presented the first fully electronic decentralized system with parallel cabling.

Since then, the intercoms have evolved and are now used well beyond their original functions. The development of the intercom was at times ahead of the telephone. For example, integrated circuits and microprocessors were used in intercom systems much earlier than in telephones. Some of the features introduced in telephones today have been standard on intercom systems for decades.

Modern IP-based intercom systems can not only transport voice, but also data and information and execute complex control mechanisms (for example at security control centers).

Modern intercoms

Control station of an intercom with direct dialing buttons for selecting conversation partners or for controlling contacts such as doors and cameras
Categorization of intercoms according to different characteristics

Modern intercom systems ( e.g. clean room , industrial, emergency call stations) can be operated with full duplex and DSP support (for quiet environments) or with voice scales (for loud, difficult environments). The connection to the call stations is made via copper cables, fiber optic cables , IP networks or wirelessly by radio . Speech communication under water, e.g. B. between mission divers and the control center, can be done either wired or wirelessly via ultrasound .

Since intercom systems are now often used in control rooms in security-relevant areas, IP-based systems usually offer many different interfaces to other systems such as video, ELA , telephone, radio, people search systems , PCs, personal emergency signal systems and building management systems.

In addition, an “intercom” system is often used in event technology to support communication between the individual areas. The intercom usually consists of several transceivers, so-called "beltpacks" , connected via XLR cables and equipped with headsets . A beltpack usually has a call function, which is equivalent to ringing a telephone, as well as an intercom function, which is primarily used.

Another area of ​​application is communication for the purpose of cooperation between aircraft crews, especially in aircraft with several crew members who work not only in the cockpit area, as was the case with combat aircraft and bombers, especially during World War II.

The use of special motorcycle intercom systems is suitable for motorcyclists .

Intercom systems are not barrier-free : the hard of hearing and deaf people who rely on lip reading cannot operate such systems.

See also

literature

  • Peter Kerger: Internal communication. Hüthig, Heidelberg 1988, ISBN 3-7785-1097-5 .
  • Herbert Petzoldt: Two-way and two-way intercom systems (=  electroacoustics, 3). Fachbuchverlag, Leipzig 1952.

Web links

Commons : Intercoms  - collection of pictures, videos and audio files
Wiktionary: Intercom  - explanations of meanings, word origins, synonyms, translations

Individual evidence

  1. Peter Kerger: Internal communication , 1988
  2. Archived copy ( memento of the original from April 24, 2017 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. @1@ 2Template: Webachiv / IABot / thw-taucher.de