Motorola ultimately settled on the identify "Police Cruiser" for his or her first police receivers, all but the primary of which were mannequin prefixed "P69", the initial drawing board providing presumably being known as solely "Police," however apparently rapidly modified to "Police Cruiser." Some prototypes are believed to exist from early 1936 which aren't identified on this listing. State police, counties and freeway patrol (and a few large metro areas) typically broadcast on the 1550-1750 Kilocycle band, while cities and small towns used the other band of 2300-2490 Kilocycles. The fundamental frequency vary of all Police Cruisers (except the P-69-17 and 17A) is 1500-3000 Kilocycles. All P-sixty nine Police Cruisers except the P-69-14 are crystal control, single channel. All fashions of P-sixty nine Police Cruiser receivers besides the P-69-14, and the very first Police Cruisers, include two vibrators; but only one is in use at any given time. Particularly aggravating for the collector and historian is that no P-69 model numbers seem clearly or commonly on the tools other than an obvious two digit number stamped on the decrease housing shell, which was easily separated from the receiver, and on the paper tag which is glued inside the lid to show parts structure. In late 1940, Motorola started promoting the "Deluxe" line of equipment, a large rounded-high two piece radio set often referred to as "coffin units," "doghouse units," or "double humpers." Although primarily an FM product, the Deluxe line apparently was supplied in a VHF AM model with a kind number AMR-13(V) for the receiver and presumably AMT-30(D) for the transmitter, but this writer has by no means run across any nor found manufacturing documentation supporting a "Deluxe" AM transmitter.

Postwar receivers generally have ink stamped dates underneath the chassis and a few of the P-69-18's comprise an inked-stamped mannequin number. Thus far, nonetheless, the efforts of the experimenters have been concentrated on telegraphy. The rapid hearth system of telegraphy is patterned after the music roll of the mechanical piano participant. As stated before, these cables' musical traits have been decisely valid and extremely attention-grabbing, contemplating the high balance between parameters corresponding to extension, refinement, warmth, dynamics and scene reconstruction confirmed either by the "Piano 6" and the "Piano 1". Considering these outcomes, I strongly counsel you do that DIY venture. And just throughout a kind of nights our "Piano 6" signal cable was delivered to gentle. Should one vibrator fail, the officer may reach down and select the other vibrator, allowing the car to proceed on patrol with out the need to return to the station for radio repairs. The opening within the case on the higher left is to permit adjustment of the antenna trimmer once the set is installed in a automobile. Other options included the "display" antenna and an extra length "super" broadcast whip. The antenna input was designed for both a standard broadcast whip or a copper "screen" antenna contained in the automobile's headliner ("tarred fabric roof" sedans), apart from 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 field assembly.

Motorola's unique antenna was a strange three-legged tripod affair as proven below and within the above photograph of a T-69-20A in a police automotive, and featured an adjustable size whip. All Police Cruisers had been primarily modified variations of Motorola's late 1930's AM broadcast automobile radios (even the "UHF" fashions !) and all are AM receivers. Police Cruisers". They should have a chrome nameplate on the entrance of the housing which says "Police Cruiser" in script, with a purple or blue painted background. The word Motorola doesn't in any other case seem on the exterior of the receiver itself, but is on the face of the control head within the type of a red painted metal nameplate. With the exception of the P-69-18SP-2, and the P-69-17 when mated with a transmitter, all Police Cruiser receivers had been initially meant to mount on the automobile firewall, behind and below the dashboard. Again, with the exception of the "SP-1 and SP-2 variations of the P-69-18 (which makes use of a "DC" electrical quantity control,) the quantity control is situated on the receiver itself and is turned through a 2 foot lengthy "speedometer" fashion jacketed mechanical cable which connects to a knob on the management head.

The earlier Police Cruisers generally have a black wrinkle finish, whereas the late-battle and postwar Police Cruisers have a blue/grey wrinkle end. Once once more, a heat thank-you to Andrea, and for you all: have nice enjoyable! Single vibrator. Color end is believed to have been gray wrinkle. It's a typical mistake to assume the 1-2 switch on the face of the housing refers to channels, nevertheless it refers to the vibrator in use! A switch which protrudes by way of the entrance panel selects the vibrator. Searching for designs that can best treat the delicate musical signal, we regularly enterprise in direction of DIY projects which are pretty troublesome and not at all people's stage. The duplexer, a tough trying machine for the delicate work in hand, is a pair of wheels driven together by a belt from a motor and touched by copper brushes. Stockton then did such efficient work that the system was accomplished. 8) on the cable's different finish, utterly get rid of the shielding, slicing both the aluminum foil and the copper braid, then join every thing to the RCA plug until you reach the external sleeve edge, soldering the Red/BLACK pair to the optimistic pole and the Green/ORANGE pair to the unfavourable pole; 9) repeat steps 1-8 for the other cable, and you are accomplished! Then, join the cables in your system, with the shielded plug to the source facet, and permit a couple of day of burn-in earlier than proceeding to a vital listening.

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