Fig. 299 - One of the first mobile radio telephony system used for police application purpose.
For historical allocation purpose the concept of mobile radiotelephony started before the turn of XX century when Thomaz Alva Edison demonstrated by the first time a system which permitted telegraphic communciation between a moving train and a base station, without requiring physical connections. As aforementioned in the Edison’s system it was used telegraphic signals only. Therefore, it was not until two decades later the first mobile radiotelephony systems were adopted for transmitting messages from fixed points to moving vehicles. Police department were among the first to use this means of communication.
Messages were transmitted by radio frequencies just above the AM broadcast bands that were picked up by receivers in the patrol cars. Since the vehicles were not equipped with transmitters, patrols car crews’ had to reply by land telephone, generally fixed in strategic points in the city. Fig 299
Radio amateurs contributed greatly to the
Fig 299A -Mobile radio telephony system used by the British police circa 1960.
improvement of mobile radio as based in their considerable experience operating in 5 and 10-meter band the same was extended to the developement of the first mobile transmitters in the 30 and 40 MHz.

In the early system the transmitter operates in amplitude modulation while some sets used superregenerative receivers. But, crystal-controlled superhetorodyne units soon outmoded these types of equipments.
Shrotly after WWII the manufacturers launched in the market frequency modulation Mobile radio equipment.
The mobile radio equipment had many applications either for military as well as civilian purposes arisen several types of services which specific frequency allocations. Among them the citzen band, in the 11 meter band or 27 Mhz that facilitate so much two way mobile communication for business of pleasure by operators without any technical knowledge such as physicians, engineers, taxi drivers, farmers and so forth. Fig. 300
As aforementioned amateur radio played a very important part through all the years of the development of radio. The knights of the ether stand as contributors to progress alongside the technical giants, the great industrial laboratories, government projects and university researches in such way the radio receiver became a popular instrument.

Fig. 300 - Several types of radio receiver used for citzen band application.
Fig. 300 - 14 channels transceiver model BB-12 made by Hallicrafters Company in the USA.  
Móbile citzen band three channels transceiver made by Midland in the USA.