Great Britain developed a variety o agency radio stations during the war. The most often used types included MARK III, MARK V, MARK VII PARASET, MARK XV, 3Mk.I-B and 3 Mk. II-B. Polish factory in Great Britain produced the agency radio stations of A-2, AP-5 and OP-3 types. Technician of Military Radio Centre, WO Antonín Šimandl designed a ŠIMANDL transmitter and MARJANKA receiver which were also used by some air-drops. Equipment of the air-drops was gradually improved. The groups of the third wave of the air-drops (1944/1945) were equipped by two sets of radio stations. One station was of a lower power but easy portable (MARK V in a case, 3 Mk. II-B2 or Polish AP-5) and the other station of higher power, used for the operation using electric network (ŠIMANDL transmitter with MARK V receiver).