Motorola hard wire hands free kit: mute line setup

I've just bought the hard wired hands free kit for my StarTAC phone (the one with the speaker under the dash & mic on the A column near the driver). I'm having it professionally installed next week. My question is: does anyone know if this kit has a stereo mute line? I read through the documentation and didn't see anything except an 'unused' orange lead.

I serached under 'motorola' on the BBS but didn't find anything specific to this. Also, if there is a mute line, how do I tell if it needs a "pull up" resistor? If it needs one, how precisely do I wire it? I figure telling the Verizon installers is not worth the time & confusion, just let them do their job by the book then do my custom tweaks later to tie it into the amps and/or empeg.

Any comments/help greatly appreciated. Thanks.

-Zeke

just say you weren't paying much attention...

I have no idea of if the kit has a mute output or not. Nor do I have a phone kit in my car, but I do have a fair grasp of the electronics involved...

If it has a mute output, it can do essentially three things:

1) Switch from 0 to 12V, or 12 to 0 when muting. This is no problem, just tell your unit which is which via emplode.

2) Normally sit at 12V and go to high impedance (essentially disconnected) or vice versa. In this case you need a pull down resistor.

3) Normally sit a 0V and go to high impedance (essentially disconnected) or vice versa. In this case you need a pull up resistor.


A pull up or pull down resistor goes between the line in question (phone mute) and 12V or GND depending on if it is pull up or pull down. (12V for up and GND for down) Best place to apply this is probably at the ISO connector (if you have one). With a really small screwdriver (watchmaker style), or the back end of a small drill bit, you can normally press back the retaining tab to the metal contacts in the connecter (from the front) so that they can be pulled out (from the back of the connector). There is normally enough place in the connector so that you can solder the leads of the resistor to the rear of the contact (which crimps on to the wire). Keep the leads parallell to the contact and don't overdose on heat. Protect the leads with electric tape or shrink tubing. Carefully bend out the retaining tab(s) again and insert the contacts into the connector. Probably a good idea to tape down the resistor to the body of the connector...

Normally a good value for the resistor is 1 - 10kOhm, but that can vary. Check the documentation for any informations as to the current capabilities/needs of the mute output! A 10kOhm resistor will make the current ~1 to 1.5mA, a 1kOhm ~10 to 15mA.

/Michael

Thank you. Once I have it installed I'll be able to test the mystery orange line with a voltmeter to see what it's doing (if the installers don't know) and then follow your instructions. I"ll post when I have it all sorted out (or get stuck!).

-Zeke

just say you weren't paying much attention...

Also see this thread which indicates that the Motorola kits need a pull up resistor.

"The line floats low which means that if you have a phone sense that connects the line to zero volts you will need:

1. A 10K pull up resistor between the mute sense line and twelve volts."


"The Motorola car-kits are pull-down, so I guess you'll need a pull-up on the control line"


/Michael

The rio-car includes this resistor internally ISTR, so it's only needed on empeg boxes.

Hugo

And that should be detectable as +12V existing on the phone mute line, instead of floating low as said in the old thread referenced above, or?

/Michael

Well, after talking with the lead installer at the wireless shop (Verizon) it looks like this hands-free install has no stereo mute line at all. The unidentified wire is a horn remote to make the horn blow when the phone rings (for contractors/surveyors and the like). Looks like I'm on my own on this one, I'll probably try and tap into the little speaker's wire to see what sort of voltage it's got, maybe I can rig a relay setup somehow...we will see. I'll post what I find.

-Zeke

just say you weren't paying much attention...

Should be, yes.

Hugo

sb knowing how to deal with a panasonic G600 handsfree kit? my mute cable is professionally mounted but not working (when I switch in emplode (12v...), it's ever mute or never. ???

__________________________

David Clesse
Belgium/Luxembourg
Mk2-36g(full)-red-tuner-stick

Do you have MkII or MkIIa? As per above, MkIIa's should be OK as they're (all?) fitted with an internal pull up resistor... But it does sound like you're a candidate for a pull up or pull down resistor...

Try to measure what the handsfree kit is doing (unplug it from the empeg if possible) and apply resistor as described above in the thread.

/Michael

The input floats low (ie, 0v). If your mute line pulls to 0v when the phone is active and you have an empeg (mk2) player then the behaviour will be as you describe.

Put a 1k resistor between 12v (eg, orange wire in empeg harness) and the mute line. This will ensure that when the phone isn't muting, the line will be at 12v and the empeg should continue playing. When the phone becomes active, it will easily overpower this resistor and the empeg will see 0v and mute.

Hugo

Maybe during installation they put a pull up, and it should be a pull down? I kept the empeg, I just give them the tray & docs. What I'm sure is that I seen a resistor.
Can I try to inverse the resistor, without risks?

If it's not that, I'll try your solution. Sorry but I'm not very comfortable with electrics. tnx. David.

__________________________

David Clesse
Belgium/Luxembourg
Mk2-36g(full)-red-tuner-stick

Yes, resistors aren't polarised. Check first they have put a pull down (ie, the resisitor goes between mute and ground) and then disconnect the ground and and connect it to 12v.

Hugo