Manual LB system

Inventory number: T99 1/6/1
Location: Hall 1

The first generation of the telephone exchanges has been based on the manually switched LB principle, where the connections were made by operators, and each subscriber telephone set needed its own power supply, a so-called local battery. The notion of this system became popular by the initials LB of the English denomination Local Battery. The <<908>>Leclanché cells<> powering the microphone, and later the dry batteries, were placed in the box of the telephone set or in a separate battery box. The LB system had several disadvantages: the local batteries require permanent maintenance, the subscriber must turn the inductor lever at the beginning (end even at the end) of the call, the termination of the conversation can be observed only by monitoring the call by the operator, etc. Initially, the crossbar-type jack fields (telephone exchanges) were operating in a single-line system. The speech apprehension was difficult because of the inherent cross-talk of the system and the different electrical perturbations. The network development has thus led to the use of two-wire exchanges. This picture shows the telephone exchange in Baross street. Standardized exchange types were LB 10, LB 25 and LB 100, with the numbers referring to the line capacity. In the case of local exchanges connecting more than 100 subscribers, several switching cabinets were placed side by side and were multiplied. The firs two-line exchange has been built 1896 in Temesvár with 660 subscribers, followed 1897 by the exchange with 3000 subscribers in Szerecsen street in Budapest. From 1928 on, the so-called vertial* LB exchanges were being used. In smaller settlements and villages the LB-type exchanges continued operating till 1996.

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