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The one piece TR 20-18 set proven right here was utilized by the Tracy, California Fire Department in a hearth engine and was licensed as a police transmitter, into the late 1940's. It accommodates a P-69-18 receiver and a T-69-20A transmitter. As an aside, the above management head, last produced in approximately 1949, was still in use by the Los Angeles Police Department even in1960, and probably past, working a customized made cell radio with a low frequency AM receiver and a VHF transmitter. The P-8022 control head above was typically used with the "one piece" set up proven above it, however not with the original T-69-20A installations, which used separate management heads for transmitter and receiver. It seems there was also a TR 20-13, an earlier model utilizing the P69-thirteen receiver. This appears to have been Motorola's only AM cell transmitter, and is a two piece set during which the facility provide and modulator are in a single case and the RF section in a second. This management head was primarily used with the "Deluxe" line of FM tools, launched in late 1940. Also be aware that coiled microphone cords are a postwar growth. As well as, the rear "hang-up button" was a wartime growth.

During wartime and to the end of Police Cruiser production, a sort of "one-piece" two-means radio set was manufactured, which consisted of both T-69-20A transmitter circumstances and a P-69-18 or -17 Police Cruiser receiver, all mounted on a big copper plated chassis, which was mounted in the trunk compartment of a police automotive or in a utility compartment on a hearth engine. The control head is the P-8022 as used on wartime and postwar Deluxe Line FM sets. A few of the earliest postwar 2-approach California Highway Patrol installations started out with a Police Cruiser receiver, and added both Motorola and RCA 39 Megacycle VHF FM transmitters later, within the case of the RCA by modifying the RCA management head to function the P-69-18 Motorola receiver ! The later variations of those sets used the P-8022 control head for each receiver and transmitter capabilities whereas earlier used the separate heads of each component. The SP-2 is already wired this way and was mainly meant to facilitate the addition of a transmitter to the cellular installation and placement of the receiver in the vehicle trunk compartment.

For some motive the orientation of the receiver appears to have been altered. The best way to think about them is to their low voltage energy cables factory, and you'll know if they've the power to offer the required cable. A moderately thick cable delivered the excessive voltage and other strains back to the trunk, beneath the flooring mat. One platform only mounted a T-69-20A transmitter and its energy supply within the trunk, with out a receiver (which was nonetheless sprint mounted, thus not really a "one piece" set.) The unique platforms often contained legs to allow them to be suspended in the auto trunk, subsequent to or above the spare tire. The first Motorola AM cell transmitter was the T-69-20A. For example, they have been used within the trunks of Signal Corps staff vehicles for the 1940 annual War Games at Camp McCoy, Sparta, Wisconsin (believed to be P-69-17A / T-69-20A combos, (in a TR 20-17 setup.) Advertisements in CQ Magazine within the late 1940's by surplus sellers provided these as having come from "navy police service." There were several sorts of steel platforms used to mount these "one piece" units. Both of those modifications distant-wired the amount management in order that it could be managed at a separate control head, electrically, and had been primarily intended to allow mounting the Police Cruiser within the vehicle trunk.

The T-69-20A was introduced in August, 1939. Production continued by means of approximately late 1949. The management head was out there as a "handset" kind, by which a push to speak Western Electric "E" sequence phone handset hung alongside or on a cradle on top of the control head, low voltage armored power cable which was a grey sq. field with Amphenol connectors on the underside for the management cable connections. This was the usual management head for the T-69-20A although there were at least two other kinds which have been earlier, such because the one proven within the photograph above, which has the connector on the bottom apron, and one other, upon which the cradle for a Western Electric "E" fashion handset was hung. There have been a minimum of two variations of T-69-20A management head fashion. Produced a minimum of by means of 1949. The knobs are the same as shown on the P-69-12 above. This cowl is friction-fit only, there are not any screws securing it as on different models. Shown beneath is an unusual, apparently early P-69-18 with a blue nameplate and a handle on the upper cowl. The photograph under shows a typical early P-69-18 with a black housing and a purple nameplate. See typical T69-20A installation photograph under. The -SP2 modification includes the -SP1 modification, but additionally permits trunk mounting of P-69-18 by including a cable connector box (see picture below) which allows the receiver to interchange with a Deluxe Line FMR-13V VHF FM receiver and be compatible with an FMTR-30D radio accessory set.