The Echo 231-Z radio is a luxury, four-valve reaction receiver, allowing reception of radio signals in the short, medium, and long wave bands. It has two circuits and a built-in electrodynamic speaker. It was equipped with tone controls and reception strength adjustment, and it also has a scale, a built-in antenna and sockets for connecting an additional speaker and adapter. The radio’s electrical system is placed in an elongated, painted walnut box in the shape of a cabinet with two-leaf doors.
The Echo 231-Z was produced from 1936 and cost 297 zlotys. Państwowe Zakłady Tele- i Radiotechniczne (PZT) also manufactured similar designs named Echo 232 and Echo 241 (both with roller doors). There were also other radio models sold under the common name Echo that were assembled from Polish components. Some of the models were made for the purposes of the postal service and on a commission from the Minister of the Interior (these were the so-called “municipal radios”).
The PZT was established in 1932 as a result of the merger of the Państwowa Wytwórnia Łączności and Państwowa Wytwórnia Aparatów Telegraficznych i Telefonicznych. The factory was located in Grochowska Street in Warsaw. Originally the establishment repaired telegraphic and telephone equipment, and production of the telegraph, telephone devices, and telephone switchboards was launched later. In 1939, the PZT was Poland’s largest and most modern radio technology production plant. In particular, it specialised in the production of specialist broadcasting and radio technology equipment. The factory produced aviation and naval radio communication equipment for the domestic and export markets. Contrary to large companies such as Elektrit and Philips, the PZT did not work on a seasonal basis. Models were manufactured for years, most of them under the common name of Echo. The name was followed by a group of two or three digits and a letter: the first digit meant the number of tuned circuits, the second – the number of tubes, the third – the symbol of the consecutive type in the group. The letter signified the type of power supply: Z – AC, S – DC, B – battery power.
The PZT owed its development to designs developed at the Studies Bureau, in which inż. Wilhelm Rotkiewicz, the creator of the famous Detefon, worked. The plant supported the Polish industry, not only by using Polish components for the assembly of its devices, but also by using appropriate advertising slogans for its products. One example is the poster for the 231 model of the Echo series, with the slogan: “Money paid for the Echo – STAYS IN POLAND”.

Authors: Piotr Turowski, Filip Wróblewski