Telephone Installations  Manufacturers, Traders, Suppliers

In industrial telephone systems, telephone, fax and call advisors are connected to each other and to the public telephone network. In order to achieve this, a switching network is used, in which input and output channels are switched by a control unit. Telephone systems are devices for switching several terminals such as telephones, fax machines or answering machines. These can be arranged among each other, but also with the public telephone network. A fundamental component for fulfilling these tasks is the so-called coupling network. Its task is to switch the input and output channels by a control unit. A great advantage in the use of such a system is the free use of a connection between connected end devices and thus a better use of the free exchange connections since a subscriber line does not have to be laid for every device. Also the possibility of the further connection of telephone calls, switching, call diversions is a large advantage. Usually there is a so-called query station, where the calls are answered centrally. After this acceptance the mediation usually takes place to the desired person. A telephone system also offers data on the billing of telephone calls and records corresponding data and logs according to time and telephone number of the outgoing or transacted telephone calls. Control over calls from individual extensions is also possible. The extent to which these can be reached from the outside is checked. The switching of internal and external calls is usually carried out via a single-digit or multi-digit prefix, the traffic discriminating digit. In Germany, the traffic excretion number 0 is often used. This can have various functions. For example, if 0 is dialed, no official call can be made and a busy signal sounds. This is then referred to as the non-authorized method. With the semi-authorized variant, an extension can be called from external parties, but cannot automatically make calls to the outside world. External calls may have to be approved by the interrogator. The local function becomes effective as soon as the extension is able to dial 0 and thus only make local calls. Fully authorised telephone systems are also operated without restrictions for all extensions.