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The one piece TR 20-18 set shown 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 contains 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 presumably past, working a custom made mobile radio with a low frequency AM receiver and a VHF transmitter. The P-8022 control head above was often used with the "one piece" set up proven above it, but not with the unique T-69-20A installations, which used separate management heads for transmitter and receiver. It appears there was additionally a TR 20-13, an earlier model utilizing the P69-13 receiver. This appears to have been Motorola's only AM mobile transmitter, and is a two piece set during which the power provide and modulator are in one case and the RF section in a second. This control head was primarily used with the "Deluxe" line of FM tools, launched in late 1940. Also word that coiled microphone cords are a postwar development. In addition, the rear "hang-up button" was a wartime improvement.

During wartime and to the top of Police Cruiser manufacturing, a form of "one-piece" two-way radio set was manufactured, which consisted of each T-69-20A transmitter cases and a P-69-18 or -17 Police Cruiser receiver, all mounted on a big copper plated chassis, which was mounted within the trunk compartment of a police car or in a utility compartment on a fireplace engine. The control head is the P-8022 as used on wartime and postwar Deluxe Line FM units. Among the earliest postwar 2-manner California Highway Patrol installations started out with a Police Cruiser receiver, and added each Motorola and RCA 39 Megacycle VHF FM transmitters later, within the case of the RCA by modifying the RCA control head to function the P-69-18 Motorola receiver ! The later variations of these units used the P-8022 management head for each receiver and transmitter capabilities whereas earlier used the separate heads of every part. The SP-2 is already wired this manner and was mainly supposed to facilitate the addition of a transmitter to the mobile set up and placement of the receiver in the automobile trunk compartment.

For some purpose the orientation of the receiver seems to have been altered. The best way to think about them is to their low voltage energy cables manufacturing facility, and you can know if they have the flexibility to supply the required cable. A quite thick cable delivered the excessive voltage and other traces again to the trunk, underneath the flooring mat. One platform only mounted a T-69-20A transmitter and its energy provide within the trunk, without a receiver (which was still 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 primary Motorola AM cellular transmitter was the T-69-20A. For instance, they had been used within the trunks of Signal Corps workers cars for the 1940 annual War Games at Camp McCoy, Sparta, Wisconsin (believed to be P-69-17A / T-69-20A mixtures, (in a TR 20-17 setup.) Advertisements in CQ Magazine in the late 1940's by surplus sellers supplied these as having come from "navy police service." There have been a number of forms of steel platforms used to mount these "one piece" sets. Both of these modifications distant-wired the amount management so that it could be controlled at a separate management head, electrically, and were primarily intended to allow mounting the Police Cruiser within the car trunk.

The T-69-20A was introduced in August, 1939. Production continued by way of roughly late 1949. The control head was out there as a "handset" kind, through which a push to speak Western Electric "E" collection telephone handset hung alongside or on a cradle on high of the management head, low voltage armored power cable which was a grey square box with Amphenol connectors on the bottom for the control cable connections. This was the standard control head for the T-69-20A though there have been not less than two other styles which were earlier, such as the one proven within the picture above, which has the connector on the underside apron, and one other, upon which the cradle for a Western Electric "E" style handset was hung. There have been at least two variations of T-69-20A management head fashion. Produced no less than by way of 1949. The knobs are the identical as shown on the P-69-12 above. This cowl is friction-fit solely, there are not any screws securing it as on different models. Shown under is an unusual, apparently early P-69-18 with a blue nameplate and a handle on the higher cowl. The photo under exhibits a typical early P-69-18 with a black housing and a crimson nameplate. See typical T69-20A installation picture under. The -SP2 modification includes the -SP1 modification, but also permits trunk mounting of P-69-18 by adding a cable connector field (see photo below) which permits the receiver to interchange with a Deluxe Line FMR-13V VHF FM receiver and be suitable with an FMTR-30D radio accessory set.