geographical oddities, including a number of exclaves and enclaves that Greater Berlin had inside some neighbouring municipalities since 1920, all of which happened to become part of the British or American sectors after 1945, so that parts of West Berlin came to be surrounded by East Germany. Furthermore, the Gatow/Staaken exchange in August 1945 resulted in the geographically western half of Berlin-Staaken, which was located in the western outskirts of the city, becoming de jure Soviet occupied. However, the de facto administration remained with the Borough of Spandau in the British sector. Therefore, all inhabitants of Staaken could vote in West Berlin's city state elections in 1948 and 1950. On 1 February 1951, East German Volkspolizei surprised the people of western Staaken by occupying the area and ended its administration by the Spandau Borough; instead, western Staaken became an exclave of the Soviet occupied borough Berlin-Mitte in the city centre. However, on 1 June 1952, western Staaken's de facto administration was placed with neighbouring East German Falkensee in the East German district Nauen. This situation was undone on 3 October 1990, the day of German unification, when western Staaken was reincorporated into united Berlin. Post and telecommunications West Berlin had its own postal administration first called Deutsche Post Berlin (1947–1955) and then Deutsche Bundespost Berlin, separate from West Germany's Deutsche Bundespost, and issuing its own postage stamps until 1990. However, the separation was merely symbolic; in reality, West Berlin's postal service was completely integrated with West Germany's, using the same postal code system. West Berlin was also integrated into the West German telephone network, using the same international dialling code as West Germany, +49, with the area code 0311, later changed to 030. Unlike West Germany, from where calls to East Berlin were made using the prefix 00372 (international access code 00, East German country code 37, area code 2), calls from West Berlin required only the short code 0372. Conversely, those made to West Berlin from East Berlin only required the short code 849. In order to reduce eastern wiretapping of telecommunications between West Berlin and West Germany, microwave radio relay connections were built, which transmitted telephone calls between antenna towers in West Germany and West Berlin by radio. Two such towers were built, one antenna in Berlin-Wannsee and later a second in Berlin-Frohnau, finished on 16 May 1980 with a height of . This tower was demolished on