>>>2024-05-07 Electrical Characteristics Of Telephone Lines (PDF) > 자유게시판

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This seems to have been Motorola's solely AM mobile transmitter, and is a two piece set by which the facility provide and modulator are in a single case and the RF part in a second. It's also believed that assorted particular variations were made to buyer order, equivalent to non-commonplace energy provide inputs, mounting schemes and so forth. Both of these modifications remote-wired the volume control in order that it would be controlled at a separate control head, electrically, and were primarily intended to allow mounting the Police Cruiser in the vehicle trunk. The -SP2 modification contains the -SP1 modification, but also permits trunk mounting of P-69-18 by adding a cable connector box (see picture below) which permits the receiver to interchange with a Deluxe Line FMR-13V VHF FM receiver and be compatible with an FMTR-30D radio accessory set. I am searching for other examples of previous police radio equipment from the 1930's and 1940's - - do not let this tools wind up on the landfill! The one piece TR 20-18 set proven right here was utilized by the Tracy, California Fire Department in a fire 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.

Shown below are the usual speedometer cable style "distant" control head for the P-69- sequence Police Cruiser receivers which didn't characteristic electrical quantity control, specifically the P-69-12, thirteen and 18, and the "small" cellular speaker. The brand new volume management was then a DC remotely managed design moderately than the speedometer style cable of earlier models. This cover is friction-fit only, there aren't any screws securing it as on different fashions. There have been not less than two variations of T-69-20A control head style. Produced at the least by 1949. The knobs are the same as proven on the P-69-12 above. Somewhat frequent. The squelch control was moved to the entrance panel and supplied with a knob, in contrast to previous variations, the place it was positioned behind a plug button on the facet of the housing, as proven on the P-69-thirteen above. Shown beneath is an unusual, low voltage armored power cable apparently early P-69-18 with a blue nameplate and a handle on the upper cowl. There was also a "giant" cellular speaker, featured in the photo of the transmitter set up shown later on this page.

The photograph under reveals an early P-69-17 with the identical control head as the opposite Police Cruisers which had been crystal managed. The picture below reveals a typical early P-69-18 with a black housing and a crimson nameplate. These had been shipped in a black wrinkle color scheme until someday after 1945, when the shade was switched to gray wrinkle. Single channel. Exterior black wrinkle enamel. Selectable twin vibrators. Exterior blue-grey wrinkle enamel on SP2. Crystal control, twin vibrators. Crystal control, single channel. Operated within the 30-40 Megacycle range, crystal control. The head for the P-69-17A added a toggle swap for squelch between the pilot lamp and the quantity management. Any submissions may be added to this and different net pages I am creating. The distinction does not really matter that a lot on the telephone finish, however will be complicated if you're taking a look at documents that use totally different conventions. Historically splice cabinets have been typically mounted up utility poles, however this made them tougher to safely work on so this association is pretty much gone to historical past. Second, splice closure and cabinets are deliberately made for easy modification. Instead, fashionable splice cabinets are larger floor-stage pedestals, normally an excellent 4-eight ft large with large double doors.

For overhead wiring, splice closure are normally black plastic cylinders hung alongside the cable. Once your telephone loop makes it out of your cellphone, via your own home wiring, down a drop cable, by means of an F2 cable, and then via an F1 cable, it arrives at the telephone change. In the event you crack open a wall and have a look at your household telephone wiring, you will nearly definitely discover a stunning variety of wires. This is one of the differences you will find when you look in other countries: as a result of of exact particulars of the electrical design of the alternate and the telephones, and the place totally different parts are positioned, some international locations such because the UK require slightly more complicated household wiring than simply putting all jacks in parallel. If the issue goes away, it is someplace in your family wiring, and subsequently not the phone company's drawback. You would possibly expect some hefty ISO specification for analog telephone lines, however there is not really one outdoors of tools specifications published by manufacturers.