In Yugoslavia's all-people defense system, the internal affairs agencies were part of the armed forces. In their work they used numerous communications devices, some of which are described here, covering the period from World War II to 1991, which this website covers. For easier understanding, some important details from the history of the internal affairs agencies are noted below. Also, although the term "police" (from Greek πολιτεια — state administration, state affairs, the branch of state authority responsible for public order and peace) was not used during that period, we will use it on this site as a shorter and more widely known term.

Unlike the military, whose organization and jurisdiction covered the entire Yugoslav territory, the police were organized in a decentralized manner on a territorial basis. Accordingly, republican laws (and from the constitutional changes of 1971, also provincial laws) defined the duties, jurisdictions and organization of internal affairs agencies in those territories. Changes in the organization of internal affairs were significantly influenced by the political situation in the world (for example, the deterioration of relations with Warsaw Pact countries in 1948, following the Cominform Resolution) and domestically (for example, the Brioni Plenum of 1966). Funding was local, at the municipal level, which also affected the equipment of internal affairs agencies.

Even during World War II, on the liberated territories, the first agencies were formed for securing the rear and maintaining public order and peace. These agencies had various names: people's, village and partisan guards, or people's militia (Lat. militia — military service, people's army, armed people). On May 13, 1944, the Department for the Protection of the People (OZN) was formed, and in August of the same year the Corps of the People's Defense of Yugoslavia (KNOJ) was formed from NOVJ members, representing the operational units of the OZN. This date was celebrated as Security Day.

Immediately after the liberation of Belgrade, training of the first members of the People's Militia began. Initially, militiamen performed exclusively patrol, guard and escort duties, while KNOJ members and the Yugoslav Army (JA) secured facilities and institutions. The first militiamen were not uniformly dressed, distinguished only by a tricolor armband with a five-pointed star and the letters NM.

Under the 1946 Constitution, within the All-Union Ministry of Internal Affairs, the Administration of the People's Militia, Command of the People's Militia, Administration of Public Security and Administration of State Security (UDB-a, formed by transferring parts of the OZN from the JA into the All-Union MUP) were established. Military organization, uniform dress and ranks were retained. The constitutional reforms of 1953 brought significant changes. Instead of the existing ministries, secretariats were formed — the Federal Secretariat for Internal Affairs (SSUP) and republican secretariats for internal affairs (RSUP). As part of the demilitarization of the SSUP, the UDB-a ceased to be a militarily organized, uniformed service, and its operational forces KNOJ were dissolved (KNOJ's tasks were divided between the border units of the Yugoslav People's Army and the People's Militia). The People's Militia retained ranks whose insignia were changed; militiamen were allowed to wear civilian clothing off duty and service numbers were introduced (on nickel-plated belt buckles). Equipment and armament were very varied, as the militia was equipped with captured weapons or equipment from Allied aid.

Increasing decentralization led to a new reorganization of the service in 1956 with the adoption of the first Law on Internal Affairs Agencies. A large part of responsibilities was transferred to the republics and administrative-territorial units. The constitutional changes of 1963 and the Basic Law on Internal Affairs Service of 1964 continued decentralization, with the basic internal affairs agencies formed at the municipal level.

After the Brioni Plenum of 1966 (at which Aleksandar Ranković, the then-federal minister of internal affairs and Vice President of the Republic who headed all police and secret services of Yugoslavia, was dismissed), major changes took place, formalized by the Basic Law on Internal Affairs of 1966. The previously established unified system of state security of Yugoslavia was dismantled. Internal affairs were concentrated into two services: the Public Security Service (SJB — Militia, Crime Suppression, Traffic Safety and Border Affairs) and the State Security Service (DB, later SDB). The People's Militia was renamed Militia; numerous personnel and organizational changes were made (the Militia was incorporated into the SJB); ranks were abolished and function insignia were introduced (worn similarly to ranks but indicating the function performed by the internal affairs member).

With the constitutional amendments of 1971, the Constitution of 1974 and the laws enacted under the new Constitution, decentralization continued. Equipment and armament procurement became the responsibility of republican and provincial secretariats. The agencies of the autonomous provinces of Vojvodina and Kosovo and Metohija operated under provincial laws, although they were part of Serbia. Unlike the state security services which remained organized at the republic and provincial level, the public security services aligned with the concept of social self-protection and a fragmented security system (further decentralization). Essentially, the relations between the federal and the republican and provincial secretariats were based on the principle of agreement, cooperation and coordination of work, not on the principle of hierarchy and subordination. This decentralized system with non-professionalized elements showed numerous deficiencies as early as 1972, during a terrorist group's incursion into Yugoslavia. Based on that experience, legal amendments of 1972, 1977 and 1979 led to the establishment of special anti-terrorist units of the MUP (Ministry of Internal Affairs), as well as the first police operational pursuit groups. In accordance with the constitutional changes and reorganization of internal affairs agencies, function insignia were abolished and professional rank insignia were introduced.

This decentralization, varying legal solutions and large differences in funding led to significant differences in the organization and equipment of internal affairs agencies. At the federal level there was the Federal Secretariat for Internal Affairs. At the republican and provincial levels there were republican and provincial secretariats for internal affairs. At the regional levels there were various agencies, depending on which republic or province was involved (SUP — Secretariat for Internal Affairs, ZSUP — Joint Secretariat for Internal Affairs, MSUP — Intermunicipality Secretariat for Internal Affairs, CJB — Public Security Center, CB — Security Center). At the municipal level, depending on the size of the municipal territory, there were the Department of Internal Affairs (OUP), Militia Station (SM), Militia Department (OM) and similar.

Regarding communications, communications duties at the municipal level were performed by semi-professional signals operators (usually militiamen from the Duty Service, trained at appropriate courses), while at regional and higher levels there was an organizational communications unit (section, department, directorate) with professional personnel. All communications systems were represented, but their application differed somewhat from military use. Telegraph and telephone communications systems, radio-relay and shortwave radio systems were operated by professional signals operators. The situation was quite different for radio-telephone communications (VHF and UHF): the systems were installed and maintained by professional signals operators, but were most used by uniformed members (militia) and the civilian operational staff of the Public Security Service.

To even be able to form and maintain communications systems in such a situation, at the federal level there existed an Interagency Commission where agreements and recommendations were reached on the further development of communications. At the republican and provincial levels there were Communications Committees, whose members were communications directors (in larger centers the Department Chief, in smaller ones the Head of the Communications Section) and the deputies of the heads of all regional agencies (SUP-MSUP-ZSUP) or assistants to the head responsible for the Public Security Service. Also, committee members included communications directors and one official (undersecretary or assistant secretary) of the republican or provincial secretariat. This committee reviewed all communications issues and made decisions on further development and communications problems. An Equipment Standard existed, agreed upon and adopted by the Committee. The Standard prescribed minimum quantities of communications equipment and devices by type, for internal affairs agencies at all levels. In addition, the Committee made decisions on simultaneous equipping with one type of equipment, enabling efficient functioning of the communications system. Taking into account the state of a communications system, procurement or replacement priorities were determined by year, and all had to adhere to these priorities (one year, for example, everyone procures electronic teleprinters; the following year everyone procures special telephone exchanges; another year everyone procures HF radio stations, etc.). Equipment of the type and quantity defined by the Standard had to be possessed by all, while more than that could be procured in accordance with their needs and financial capabilities.