Pyongyang Trolleybus Factory
The Pyongyang Trolleybus Factory (PTBF) is an automotive industry company in North Korea and is the largest trolleybus manufacturer in the DPRK. During its existence, it has also manufactured vans, refrigerated trucks and buses although its main product are the Chollima branded trolleybuses. It has continuously manufactured trolleybuses since 1960, when it built the first trolleybus in the DPRK, a Jinghua BK561 clone. History 
The factory began as a truck repair factory in April 1959. It would engage in truck repairing until 1969. The first trolleybus produced at the factory was built in 1960 and was a direct copy of the Chinese Jinghua BK561 trolleybus. The first serially produced vehicle, the Chollima-9.11, was first built in 1961 although still bearing a strong resemblance to the Jinghua BK561. As passenger transport with trolleybuses only formally commenced in late 1961, trolleybuses were tested on a small loop of wire at the trolleybus factory. The visit of Kim Il Sung in fall 1961 is commemorated in a large mosaic located in the factory courtyard, which depicts when he visited the factory, after the construction of a line along Stalin avenue and People's Army avenue, before the commencement of passenger traffic. Five trolleybuses were presented to him during this visit. Andrei Lankov wrote that in the mid-1980s, the factory constructed trolleybuses in an extremely crude manner, with practically no mechanisation, such as the use of stamping or pressing equipment. Workers had to shape the material by hand through the use of sledgehammers, resulting in dents on the bodywork. Electrical wiring was said to be stretched across the ceiling. During the period of fuel shortages in the Arduous March, the trolleybus factory converted diesel Karosa and Ikarus buses to electrical operation due to the scarcity of fuel, although electricity in that period was not easily available either. Many of these vehicles still run today and the electrification of these vehicles is a unique practice not seen anywhere else. From 2015 to 2017, the trolleybus factory underwent its extensive refurbishment, introducing precision tools, such as CNC mills. The assembly line became partially automated with automated electroplating, heat processing and assembly of motors, done under the goal of transforming the factory into a 'world class trolley bus manufacturer'. Plasma cutters were installed, greatly increasing the precision of work. Before the renovation, due to the lack of ability to produce electronic parts, they had to be sourced from China, leading to speculation that in the future, the trolleybus factory would only be responsible for making bodies and importing the other components. In 2021, the factory set the goal of building a machine that would help build articulation sections with higher reliability and lower manpower. Previously, articulation joints used in the Chollima-091 were copies of the Ikarus 280 mechanism, which was liable to jamming and creaked loudly in service. Export 
Although the Pyongyang Trolleybus Factory has never made an export order, the Ministry of Housing and Communal services in the RSFSR in 1989 had shown an interest in a 12-metre trolleybuses to be used in Khabarovsk during the 13th World Festival of Youth and Students. However, as North Korea was heavily in debt to the CMEA and the USSR, the vehicles were only a form of currency that was to be produced as advanced payment for hard currency. With the collapse of the USSR, the only potential export deal fell through. The trolleybus factory has advertised its products in the Foreign Trade of the DPRK magazine, most recently for the Chollima-321 in the 2019 Q3 edition of the magazine. Assistance to other manufacturers 
The Pyongyang Trolleybus Factory has also provided assistance to other trolleybus builders in the DPRK. In 2019, the factory provided assistance to the Pyongsong Transport Company in constructing three newer trolleybuses, two in the style of Chollima-321. Other roles 
The trolleybus factory has also designed other forms of transport, including infrastructure, trams and buses. Trolleybus systems of various cities were designed by the factory up until the Arduous March in the 1990s, based on Romanian and Bulgarian designs. The factory designs various machining tools in cooperation with universities. Operations 
South Korean sources state that the factory employs 5000 people over an area of 630000 square metre area. The factory is divided into the parts workshop, which builds various components such as trolley poles and other various parts, motor workshop for constructing the electrical motors and assembly workshop, where the final assembly takes place. Most of the components used in trolleybuses, such as the seats, are manufactured at the factory. Products 
Since the 1970s, vehicles have been named according to the year in which they started production. The Chollima-321 is an exception to this, being first unveiled in 2018 and the Kwangbok Sonyon is the only vehicle that does not have a model number. References

Notes 

Bus manufacturers
Trolleybus manufacturers
Industry in North Korea
1959 establishments in North Korea