MDC1200

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RuttyFF
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Joined: Wed Mar 16, 2016 5:53 am

MDC1200

Post by RuttyFF »

OK this is kinda a broad reaching subject but I'm new and want to learn.
What is MDC1200 and what can you do with it? Also what radio models can do what with it?

I hope this is allowed here
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kb4mdz
Posts: 282
Joined: Tue Oct 02, 2001 4:00 pm
What radios do you own?: Too many for the time I have.

Re: MDC1200

Post by kb4mdz »

Well, I had a long shpiel on this, then it dropped.

MDC1200 is a form of (low speed) data communications on a radio channel. Stands for Motorola Data Communications, 1200 bits per second (there was an older version, MDC600, for yes, 600 bps).

Probably one of the most common uses is PTT ID or ANI; each radio in the system gets its own 4-digit code, hexadecimal, and when the radio transmits it will send the code along too. Pretty common to have it sent at the beginning of transmission, sometimes at the end. For example, CDM1250 lets you do either, or both.

At the 'other' end (like a dispatch point, or a full console) a radio properly programmed, or a decoder, can receive and display the number, and potentially cross reference it to an alias. Like 1367 translates to Truck # 46, and 3599 translates to 'The BOSS.'

Other functions can be Selective Calling (one radio calls only another, beeps the speaker & opens up, the call-ee can then respond), Radio Check (think of an IP Ping command; the receiving radio replies to the calling radio but the user at the receiving end usually doesn't know it's happened unless they're looking straight at the radio when it happens. Last is Call Alert; Receiving radio beeps, opens the speaker & can toggle an accessory pin to turn something on or off. Similar to 2-tone paging at fire stations where the lights turn on, or a siren starts up, but MDC only takes under 1/2 second for a call, as opposed to 1 second plus 3 seconds for normal QCII paging.

Kenwood has something similar called FleetSync; GE/MA-Com/Harris too; it was called GE-Star. There are aftermarket manufacturers like Cimarron Technologies, and Midian, who make various modules. Been a while since I've visited Vertex world but I think they do MDC1200, too.

Different levels of the CDM & HT Series will do higher tier functions; CDM1250's will transmit PTT ID's & Selective & Call Alerts, but the CDM1500 has some other functions it can do; I'll have to look later, but maybe remote monitor (for example, a portable, turns on the microphone & Transmitter; lets you eavesdrop on what's happening.)

Another common use is an Emergency button, or Man-Down; almost 20 years ago I installed a Maxtrac/GM300 series base in a guard shack, which would decode the ID's of a bunch of portables & put a 2-digit # on the display; the portables also had a tilt switch so that if it went over on its side for longer than a pre-determined time, the radio would key up & send and emergency code; the base decoded it & flashed its display & beeped loudly.

PTT ID is really good for catching users who like to play around on the radio; keying up without saying anything, rebroadcasting music from the good-times radio, etc. In the last scenario, I've seen it happen that someone plays around like a DJ, their ID shows up on a decoder, radio tech says "Truck #so-n-so, this radio system is for business use only. What you're doing is illegal and against company policy. Stop it right now! Your supervisor will be notified!"


Clear enough? More ?
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fogster
Posts: 386
Joined: Sun Nov 06, 2005 10:38 am
What radios do you own?: XTS2500/5000, XPR7550/5550

Re: MDC1200

Post by fogster »

There's no way I can do better than kb4mdz, but I know sometimes I benefit from seeing the same thing explained a few different ways, so I'll offer my own answer.

In its simplest form, MDC1200 is usually a PTT ID, where it just transmits a 4-digit numeric code when someone keys up in an annoying data burst. (It's actually hexadecimal -- each digit can be 0-9, or A-F.) Normally each radio would be programmed with a unique number, so the dispatcher can know who's talking. Actually just the other day with my local police department, an officer keyed up and just said, "Start me another car!" with a lot of yelling in the background. Kind of made the hair on the back of my neck stand up. (This ended up being a mess, too. The officer was fine, but for some reason dispatch didn't have that radio ID mapped to anything, so they were unsure who was calling for help. It was pretty quickly sorted out, but it was a tense 30 seconds or so!)

A number of handheld and portable radios can actually show the ID as well. My XTS2500, for example, will show PTT IDs on the screen. I've built up an alias in the radio of what some of the IDs mean based on what I've heard, so, for example, A008 on Boston FD is Engine 4.

On analog radio systems, it's also what triggers when you press the orange emergency button -- some data bursts with your unit ID go out and indicate that you require help.

kb4mdz goes into good detail on a lot of the other things that can be done with MDC, though in my experience they're not all that widely implemented. Another one is that it's possible to "Stun" or "Kill" a radio from a dispatch console, though only if the radio's set up to do so. The idea is that if you steal a detective's radio or something, dispatch can remotely kill the radio so you don't have access to whatever encrypted channels they might have, and so you can't cause mayhem. The radio will appear to the user to be totally dead. (It can be reversed with a dispatch console as well.)
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