There was a great need in the developing industry and state administration in post-war Poland for managing internal telephone networks designed to operate in the conditions present different employment establishments (steelworks, mines, railway, administrative buildings). It was not by accident that the Telkom-Telos telecommunications equipment factory was situated in Kraków, where, in nearby Nowa Huta, an enormous metallurgical conglomerate was built as part of the six-year plan of 1950-1955. In 1958, Telkom-Telos was put under the supervision of the Ministry of Heavy Industry, and in the 1960s it became part of the Unitra Union of Electronic and Communications Technology Industry. The development projects of the 1960s and 1970s shaped the eventual production profile of the factory, which from then on produced specialist telephones for mining (spark-safe), the rescue services, railway, the commercial fleet and the navy, which were complemented by payphones, office telephones, replacement parts and components. This specific production profile allowed the enterprise to survive after the free-market transformation that took place in the last decade of the 20th century. This was because firstly, it allowed Telkom-Telos to manufacture many devices for export markets (even as much as 40% of its production was exported in different periods) – initially to Comecon countries and later also to the West – and secondly, cheap goods from the Far East could not pose a threat. Telkom-Telos is one of a handful of Polish enterprises still operating in the telecommunications industry today.
One of the specialisms mentioned above was the production of systems for business managers. The first was the ZAS system of serially connected telephones, designed in the 1970s. The TELZES1 secretary/director’s office telephone presented here was a modernised version of the ZAS. Apart from a few modifications, the model was identical to its predecessor, but the TELZES1 was given a new housing, set of switches, and LEDs instead of lightbulbs. In later units the dial was replaced by a keypad. Depending on the version, it allowed two city lines and three or five telephones to be connected. The devices had modern segment switches. The system was powered from the local telephone line, but it was also equipped with a 24V stabilised power supply unit for handling intercom calls. It was also possible to establish conference calls with all internal subscribers, as well as recording calls by connecting a reel-to-reel tape recorder.