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  #1 (permalink)  
Old 02-19-2012, 3:41 PM
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Default MDC1200 Question.

What is more beneficial? Having MDC at the beginning of the TX or the end? I would assume the beginning because at the end you must wait until the TX is over before know which radio it came from. Is this generally how it works? Thanks.
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Old 02-19-2012, 3:47 PM
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All the department's around here use it at the beginning. Seems to make sense to ID the radio right away from a dispatch perspective...although the only issue you may run into is people not giving enough time for the MDC transmission to go through (assuming the MDC ptt-side tone is muted), and subsequently cutting off the first part of their transmission.
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Old 02-19-2012, 5:19 PM
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What about digital? How does that ID? At the begginging or end? Thanks!
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Old 02-19-2012, 7:21 PM
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P25 ID is continuous during the transmission.

Pre-ID is more common on "main" channels, since it will capture a stuck mike.

Many departments use post-ID on "direct", which gives both the sender and the listeners an audible indication that "direct" has been used.
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Old 02-20-2012, 3:51 AM
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Quote:
Originally Posted by RKG View Post
P25 ID is continuous during the transmission.

Pre-ID is more common on "main" channels, since it will capture a stuck mike.

Many departments use post-ID on "direct", which gives both the sender and the listeners an audible indication that "direct" has been used.
How does it work on trunking systems? Analog?
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Old 02-20-2012, 10:05 AM
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Quote:
Originally Posted by sepura View Post
How does it work on trunking systems? Analog?
There is no MDC for trunking.

For SmartNet/SmartZone, the IDs for talking subscribers depends on the trunking format selected by the System Operator. Very much in general:

A) For "Message Trunking," there is no ID.

B) For "Transmission Trunking," the ID of the subscriber initiating the channel grant is part of the OSW that causes other subscribers to shift to a voice channel.

C) For "PTT-ID" trunking, the ID should carry through for responding units (within the dwell timer for the voice channel assignment), but not all radios will pick it up.

For Astro Trunking, similar to "PTT-ID Trunking," but all subscribers should pick it up.

For analog, ID is via MDC-1200. (Or some different coding scheme, such as DTMF.)
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Old 03-03-2012, 5:57 PM
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We have a multi-channel LTR system using MDC-1200. The radios are set up to transmit the burst at the beginning of the transmission so we can identify the radio and assigned user.

We also have various types of devices that send MDC-IDs when pressed as alerts over a (LTR) trunking system.
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Old 05-30-2012, 3:17 PM
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I prefer Post ID. Analysis shows that received voice is recognized and processed by a dispatcher before their eyes ever get to the ID Display to begin the mental name recognition. Most transmissions end during that second action or just after. If the ID shows up at PTT release, that's pretty well when the dispatcher is mentally acknowledging who it was.
Furthermore, most, if not all, Subscriber Unit Users don't wait for the beeeeeep to end before speaking. That leads to needless repetition requests which slows the intelligence transfer process.
Plus, the receiving unit doesn't get the little vestige of signalling noise in the ear, if DOS Mute is enabled, and no one hears the squawk.
Therefore, Post ID is a more efficient.
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Old 05-31-2012, 4:57 AM
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Quote:
Originally Posted by pforbes View Post
Therefore, Post ID is a more efficient.
Except when you are trying to identify who has an open mic.
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Old 05-31-2012, 7:42 AM
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You only have to wait until the radio timeouts for the ID, there isn't much you can do with the radio transmitting anyway. An interesting problem occured in my agency with post MDC ID, the users were complaining about the first 1/2 second to RX audio being cut off. Turns out the default setting for MDC DOS MUTE is 500 milliseconds. It didn't matter that the radio was set for Post ID it still squelched the radio for 1/2 second. Had to turn it off.
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Old 05-31-2012, 8:29 AM
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TOT will take care of that.
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Old 05-31-2012, 8:46 AM
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Quote:
Originally Posted by radioman2001 View Post
You only have to wait until the radio timeouts for the ID, there isn't much you can do with the radio transmitting anyway. An interesting problem occured in my agency with post MDC ID, the users were complaining about the first 1/2 second to RX audio being cut off. Turns out the default setting for MDC DOS MUTE is 500 milliseconds. It didn't matter that the radio was set for Post ID it still squelched the radio for 1/2 second. Had to turn it off.
Of course you need to turn off that 'Mute' manually. Then there's no perceptible delay and no words are lost. You even hear the first letter of the first word.
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Old 05-31-2012, 5:58 PM
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One problem with post id. User can screw around on radio then turn portable off while keyed up.. Thereby no id sent. Lets just say some officers before mdc id was implemented were less then professional on the radio.
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