building your own clearcom/telex head set
- Thread starterkoncept
- Start date
Aaron,
You say you're testing with a 24V power supply. Is this a real Telex/ClearCom supply, or just a 24V DC power supply applied straight to the beltpacks, or a homemade com supply?
If either of the latter two, it could be improper termination. For a ClearCom system to work properly, you need to have a termination resistance of 4k ohms between pins 1 and 3, or things get wonky. Too high a resistance and you'll tend to get low volume and failure of the sidetone null (possibly resulting in feedback), too low a resistance and you'll usually get feedback and weirdness such as the call light latching for 2-4 seconds and then fading out rather than going right out when you release it (this is on a ClearCom system; on Telex, the call signal works differently; since the systems are compatible, the termination resistance should be the same or darn close).
--A
You say you're testing with a 24V power supply. Is this a real Telex/ClearCom supply, or just a 24V DC power supply applied straight to the beltpacks, or a homemade com supply?
If either of the latter two, it could be improper termination. For a ClearCom system to work properly, you need to have a termination resistance of 4k ohms between pins 1 and 3, or things get wonky. Too high a resistance and you'll tend to get low volume and failure of the sidetone null (possibly resulting in feedback), too low a resistance and you'll usually get feedback and weirdness such as the call light latching for 2-4 seconds and then fading out rather than going right out when you release it (this is on a ClearCom system; on Telex, the call signal works differently; since the systems are compatible, the termination resistance should be the same or darn close).
--A
Yeah, improper termination will definitely cause oscillation--in fact, that was the one symptom of it I forgot to mention explicitly 
) It's also probably the least known/understood part about setting up a ClearCom system.
My website's currently still down thanks to the hackers, but as soon as I finish restoring the backup (it's a slow process due to my current net access situation) I'll post a link to my guide to common ClearCom troubles, which has links to a couple great free guides online that you should definitely check out (in fact, everybody who ever sets up or troubleshoots a com system should read 'em cover to cover).
--A, resident ClearCom guru
) It's also probably the least known/understood part about setting up a ClearCom system.My website's currently still down thanks to the hackers, but as soon as I finish restoring the backup (it's a slow process due to my current net access situation) I'll post a link to my guide to common ClearCom troubles, which has links to a couple great free guides online that you should definitely check out (in fact, everybody who ever sets up or troubleshoots a com system should read 'em cover to cover).
--A, resident ClearCom guru
Aaron_Parsekian
Member
PM me when it goes back up, I'd love to learn as much as I can about clearcom systems.
Still awaiting a reply from my audio tech friend. . .
Still awaiting a reply from my audio tech friend. . .
Aaron_Parsekian
Member
LX-88 said:
Yea, the guy I emailed me hasn't responded (he's very busy) Here is a copy of my email. If any of you could ask someone you know, it would be sweet!!!!
You could prolly just show them the copy of my email
Thanks!!!!
Hey Brian,
I had a quick audio question for ya. I've been trying to get an electret microphone to work with a clearcom system with no luck. This is the schematic I tried: http://photobucket.com/albums/b194/4077hawkeye/?action=view¤t=schem.jpg
Didn't work.
So my question is how do you convert a 3K Ohm microphone to have an impedance of 200 Ohms (cleacom's standard)? Should I try a simple single transistor pre?
Ug, Impedance is just one of those things I never fully understood, any help / info you could give would be greatly appreciated.
Thanks man!
Aaron
--
Aaron Parsekian KC2IAF
Aim: h4wkeyepierce
Pictures! http://photobucket.com/albums/b194/4077hawkeye/
Here's the link:
http://www.matgoebel.com/headset/headset.htm
http://www.matgoebel.com/headset/headset.htm
Looks pretty good but I think that I would prefer to place the 9V and the circuitry into a small plastid box that would act as a belt pack. Here you could actually add a PTT button and volume control.
I am not sure that having a 9V swinging in the breeze is a good idea. Firstly the battery will either catch on something and sooner (rather than later) the wires will break. Secondly, working with pyro, the last thing I want is a battery out in the open!
So for a few bucks extra I would but a small plastic project box and a belt clip.
I am not sure that having a 9V swinging in the breeze is a good idea. Firstly the battery will either catch on something and sooner (rather than later) the wires will break. Secondly, working with pyro, the last thing I want is a battery out in the open!
So for a few bucks extra I would but a small plastic project box and a belt clip.
I had a friend who was an engineer use all of the things listed; a headset I "borrowed" From Borders, and an old clear com headset from my old high school and put them together to create an awesome around the back of the head/lightweight headset. The only problem I have come across is that the gain on the mic on the headset cannot be adjusted, and when the beltpack does not have that option either, I can't use it without creating feedback on the system. Any ideas? Or do I just have to use a terribly big headset when using a system without gain control?
You may not be able to get at the gain control, but wouldn't you achieve the same result by placing an attenuator between the headset and the input?
Assuming an unbalanced headset, which most are, grab a single gang pot and wire ground to (looking from the front) the left, headset mic to the right and beltpack mic in to the centre. Probably something in the region of 10k would be about right. Will have issues if the mic needs bias power though...
Assuming an unbalanced headset, which most are, grab a single gang pot and wire ground to (looking from the front) the left, headset mic to the right and beltpack mic in to the centre. Probably something in the region of 10k would be about right. Will have issues if the mic needs bias power though...
Jay Ashworth
Well-Known Member
I was looking for the pinout for the YC-36 adapter for the RS-602, and didn't find it hear, but I want to exhume this thread long enough to put in a link for the altogether excellent "Handbook of Intercom Systems Engineering", written (at 172pp in length) by a top guy at RTS, but applicable to all types of PL systems, and freely downloadable.
If you're plinking around with comm systems of any type to any depth, you *really* oughtta read this book, it is both informative and entertaining.
www.rtsintercoms.com/us/rts/file?i=97123&lg=eng
If you're plinking around with comm systems of any type to any depth, you *really* oughtta read this book, it is both informative and entertaining.
www.rtsintercoms.com/us/rts/file?i=97123&lg=eng
