We have been using "analog" tones effectively for several years on both VSELP and IMBE digitally modulated trunked radio systems in
applications such as fire station alerting and to open Knox-Box
cabinets in fire apparatus. Without getting too technical, there is
a modification that can be done to the Astro Spectra and the new
XTL5000 radios that basically pulls discriminator audio resulting in
a consistent audio level and roll-off. It is irrelevant whether or
not the system is a single site or simulcast.
Tones on a digital system
Moderator: Queue Moderator
Tones on a digital system
Has anyone heard of this? Taken from a local group:
Lowband radio. The original and non-complicated wide area interoperable communications system
Digital audio goes through the discriminator? 
I don't know enough about IMBE or the tolerances required by two-tone paging to say whether you could obtain a pure enough tone from the radio for a tone decoder to detect it reliably, but I figured that problem lies in the vocoder.
In any case, I'm suprised Motorola hasn't added a bunch of digital I/O lines to their digital radios, that can be pulled remotely with data packets to eliminate the need for things like this.
I don't know enough about IMBE or the tolerances required by two-tone paging to say whether you could obtain a pure enough tone from the radio for a tone decoder to detect it reliably, but I figured that problem lies in the vocoder.
In any case, I'm suprised Motorola hasn't added a bunch of digital I/O lines to their digital radios, that can be pulled remotely with data packets to eliminate the need for things like this.
I believe that VSELP was used on a 3600 baud system, so analog talk groups to pass tones are possible on those systems. IMBE also is supported in some 3600 baud systems, so analog talk groups to pass tones are possible on some of those systems, too. If the author of that statement has done this on a 9600 system, i'd be more interested to hear how 
If you can contact the author to find out what system this has been taking place on, that would be helpful.
If you can contact the author to find out what system this has been taking place on, that would be helpful.
Since the primary function of an IMBE digital communications receiver is the reproduction of the complex waveforms of human speech, pure sinusoidal waveforms such as musical notes, sirens, telephone signals, and other tones might not be faithfully reproduced. In the past, console alert tones may not have been accurately reproduced through an IMBE digital system. The effects of the digital encoding and decoding processes on the pure sinusoidal waveforms of alert tones produced a signal that didn't necessarily resemble the original tones. The alert tone enhancement option eliminates many of the problems associated with reproduction of console alert tones through IMBE digital systems.
This relates to any sinusoidal tone be it to open a Knox box or whatever.
This relates to any sinusoidal tone be it to open a Knox box or whatever.
The test tone is 1011 Hz, and it is "magic" in the sense that to generate it, you don't feed a 1011 Hz sinewave into the vocoder and use the resulting bit pattern - you use a canned bit pattern that is spelled out in the APCO-25 standard, which will then generate a 1011 Hz tone.judoka wrote:I believe that the IMBE vocoder stops working on pure tones somewhere around 500 Hz. No idea how that can be entirely true because the test tone (around 1000 Hz) works.
Yes, we've had customers who want to perform SINAD sensitivity tests on an IMBE radio - they feed in 1000 Hz (or 1011 Hz), and drop the level until the SINAD hits 12 dB - which just means the bit error rate is high enough the vocoder starts to barf. We try to explain to them that they should actually MEASURE THE BIT ERROR RATE, but most of the time the folks we are explaining this to have NO CLUE about digital radio whatsoever.
Usually these are the same guys who hate any kind of computer-like user interface on their test equipment, and want knobs for everything. Those of you who have used a modern service monitor, imagine having a knob for every function - the front panel would be 10 feet tall, 6 feet wide, and would look like the mixing console from a major recording studio.
These are also the guys who want to measure deviation with a standard FM deviation meter (rather than measuring deviation at symbol time LIKE THE SPEC CALLS OUT), have no clue what modulation fidelity is, and cannot understand why they don't hear DTMF when they push the keypad on their APCO-25 radio.
They also don't seem to understand that, if they don't understand something, that maybe, just maybe, pushing that button labeled "HELP" might just be, oh, I don't know, HELPFUL.
This is my opinion, not Aeroflex's.
I WILL NOT give you proprietary information. I make too much money to jeopardize my job.
I AM NOT the Service department: You want official info, manuals, service info, parts, calibration, etc., contact Aeroflex directly, please.
I WILL NOT give you proprietary information. I make too much money to jeopardize my job.
I AM NOT the Service department: You want official info, manuals, service info, parts, calibration, etc., contact Aeroflex directly, please.
That's exactly the reason I bought autotest software for my 2670 units
I can use a trained monkey to test XTS3000, XTS5000, Astro Spectra, Astro Sabers, all day long and all he has to have is a little common sense and the ability to follow instructions.
He takes the radio out of the box, runs the software, watches thew screen for 10 minutes, presses a button or two on the test box. Either passes the radio or writes which bit fails.
If it passes the test it has been aligned to spec by the software and it then proceeds to level 1 servicing by a slightly smarter trained monkey. If it fails it is sent to the office girl who ships it off to Mot for repair.
Simple but means I don't need bench techs. Of course the SmartZone system that's what needs the techs and if there is no problems they have a look at a couple of level 2 repairs.
I can use a trained monkey to test XTS3000, XTS5000, Astro Spectra, Astro Sabers, all day long and all he has to have is a little common sense and the ability to follow instructions.
He takes the radio out of the box, runs the software, watches thew screen for 10 minutes, presses a button or two on the test box. Either passes the radio or writes which bit fails.
If it passes the test it has been aligned to spec by the software and it then proceeds to level 1 servicing by a slightly smarter trained monkey. If it fails it is sent to the office girl who ships it off to Mot for repair.
Simple but means I don't need bench techs. Of course the SmartZone system that's what needs the techs and if there is no problems they have a look at a couple of level 2 repairs.