<P> In 1966, Bulgaria presented the pocket mobile automatic phone RAT - 0, 5 combined with a base station RATZ - 10 (RATC - 10) on Interorgtechnika - 66 international exhibition . One base station, connected to one telephone wire line, could serve up to six customers ("Radio" magazine, 2, 1967; "Novosti dnya" newsreel, 37, 1966). </P> <P> One of the first successful public commercial mobile phone networks was the ARP network in Finland, launched in 1971 . Posthumously, ARP is sometimes viewed as a zero generation (0G) cellular network, being slightly above previous proprietary and limited coverage networks . </P> <P> Prior to 1973, mobile telephony was limited to phones installed in cars and other vehicles . Motorola was the first company to produce a handheld mobile phone . On April 3, 1973, Martin Cooper, a Motorola researcher and executive, made the first mobile telephone call from handheld subscriber equipment, placing a call to Dr. Joel S. Engel of Bell Labs, his rival . The prototype handheld phone used by Dr. Cooper weighed 1.1 kilograms (2.4 lb) and measured 23 by 13 by 4.5 centimetres (9.1 by 5.1 by 1.8 in). The prototype offered a talk time of just 30 minutes and took 10 hours to re-charge . </P> <P> John F. Mitchell, Motorola's chief of portable communication products and Cooper's boss in 1973, played a key role in advancing the development of handheld mobile telephone equipment . Mitchell successfully pushed Motorola to develop wireless communication products that would be small enough to use anywhere and participated in the design of the cellular phone . </P>

When was the first handheld mobile phone invented