Community connection
In the public telephone network , the common connection refers to a technique with which several telephone connections are connected to the local exchange via the same wire pair. As a rule, it was a two-way connection , in more developed forms also dialing star connections . There were also implementations for the concentration of up to ten telephone connections. Shared connections were used wherever the network or a sub-network in the connection area did not have the required capacity. Only telephone lines in close proximity to one another and with low supply and low call volume were merged, so that the blockages remained within reasonable limits. The connected microphone units had their own phone numbers and could be reached immediately. With newer connection technology, you could also operate billing meters.
Whether the connections grouped together could make calls and establish connections with each other at the same time, depended on the type of connection technology. With two-way connections with an electromechanical connection, the participants could only take turns making calls and could not reach each other. With two-way connections in earlier carrier frequency technology (for further development see also below), as they were mainly used in Vienna, both connections could also be used independently of one another at the same time and also reach each other. With dialer connections, where up to 120 subscribers shared up to 18 lines to the exchange in Germany, and whose dialer switches initially operated with rotary dials and later worked electronically, as many participants could make calls at the same time as there were lines from the dialer switch for dialer transmission in the exchange.
The identification of the telephone connection was initially carried out in the communal changeover switches or selector star switches with the aid of electrical impulses, in the electronic versions through datagram exchange between selector star switch and selector star transmission.
Community lines are no longer used in the public communications network of the Federal Republic of Germany . When Deutsche Post the GDR was a technical variant in use, the so-called. Time party line . In Austria , so-called "quarter telephones" were used by up to four subscribers in around 40% of the telephone connections until the telecommunications networks were expanded in the early 1980s.
There is a variant that is still used today. Telephone calls can be made via both connections at the same time. A PCM2TA3 is used for this.