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The antenna input was designed for both a conventional broadcast whip or a copper "screen" antenna inside the automobile's headliner ("tarred fabric roof" sedans), except for the P-69-17 "UHF" receiver, which shared the transmitting "whip" antenna on the automobile's rear quarter panel and thus required a separate T/R relay box assembly. The one-piece set shown above included a transmit-receive antenna relay, in a small field, such that the only antenna needed can be the transmitting antenna on the rear of the patrol automobile, as in modern installations. This sensitised paper, hid in a field, is fed as tape from a roll and passes in entrance of a small hole reverse the lenses. The central collection of holes match into the teeth of a sprocket, by which the tape is led with mechanical accuracy. These pins are pressed back by the tape, however spring out when launched by the holes. Via electromagnets and vibrators the waves to which the instrument is attuned are caught and made to emit a humming sound--a short hum means a dot and an extended one a sprint. These throw on and lower off the circuit for which the receiving station is attuned.

Finally came the eventful evening when the new Federal station at Honolulu was able to speak for itself. It's an attention-grabbing undeniable fact that the brand new South San Francisco station, geared up for a regular enterprise with Honolulu in addition to inland points, uses just one thirtieth of the electric power wanted to function the spark system between the coast of Newfoundland and Ireland, which is about 400 miles the shorter distance. Clear, legible messages have been received from 200 miles over land at the speed of 300 words the minute, and from over 600 miles distance at the rate of 150. At the brand new station, the fast speaking was done with Los Angeles on the primary Sunday of its opening. The first police receivers made by Galvin in late 1936-38, earlier than the P-69 mannequin sequence. Motorola eventually settled on the identify "Police Cruiser" for his or her first police receivers, all but the primary of which have been mannequin prefixed "P69", the preliminary drawing board offering possibly being called only "Police," but apparently rapidly modified to "Police Cruiser." Some prototypes are believed to exist from early 1936 which are not recognized on this list.

AM medium wave receivers were nonetheless being produced into the mid-1950's, despite the fact that the FCC started granting VHF 30-39 MHz licenses for 2-method programs in 1936 and granted everlasting VHF licenses on both low and excessive VHF bands in late 1945. After World War Two, most manufacturers abandoned AM equipment aside from as substitute elements for present techniques. Previous to this time, Motorola had produced small quantities of cellular police receivers by modifying customary automobile broadcast radios, almost on a "request" basis for close by police departments. Police systems of the time broadcast on two ranges. Frequencies were "coordinated" into geographic zones to attenuate interference, but night-time skip conditions had change into a extreme drawback by 1940. The Fire Radio Service was not created at the identical time as the Police Radio Service and appeared some years later. Both of these modifications distant-wired the quantity management in order that it could be controlled at a separate control head, electrically, insulated copper cable and had been mainly supposed to allow mounting the Police Cruiser within the vehicle trunk. In January 1951, as a substitute for the discontinued Police Cruiser sequence, a Unichannel AM medium wave receiver strip was made out there for the brand new "Research Line" one-piece radio equipment.

No new Police Cruiser fashions had been launched after the War, although a minimum of the P69-18 was out there from current stock by about 1951. The FCC issued an order after WWII directing that all new license applications for land mobile radio providers had been to be issued a hundred and fifty MHz allocations, absent a compelling motive requiring low band or medium wave frequencies. All Police Cruisers were primarily modified versions of Motorola's late 1930's AM broadcast car radios (even the "UHF" models !) and all are AM receivers. The essential frequency vary of all Police Cruisers (besides the P-69-17 and 17A) is 1500-3000 Kilocycles. The P-69-17 sequence covered 30-forty Megacycles. After the tape has been finished, either as a information report or a collection of economic messages, it's fed right into a sending machine. Before tape is both despatched or obtained, preparations are made between stations by the odd key and receiver. The Poulsen fast receiver could also be in comparison with a shifting image taking machine.