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Radio PTT and headset wiring question


Charles Elms

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Charles Elms

 

I have a pair of Midland GTX600 FRS/GMRS radios. I also have the motorcycle helmet kit that includes speakers, boom mike and PTT switch.

 

 

Works ok for me. I would like to replace the helmet speakers with earplug speakers and replace the PTT because its fairly large for a contact switch.

 

I'm trying to figure out the wiring of the unit. I've attached a picture of the standard Midland plug for the standard mic/earpiece with PTT. The large diameter, two contact, plug is for the speaker. That leaves the small diameter plug with three contacts for the mike and PTT. I've used a very cheap digital meter and cannot detect any change in resistance across any combination on pins on the samll plug when I press the PTT. Seems like something should change.

 

I've also shown a picture of the plug on my helmet that connects everything. It's got six contact pins plus a plastic guide pin.

 

Anyone know the relationship of the pins in the helmet adapter to the pins on the standard plug? Also, how does the PTT work? If I buy a separate PTT switch, earphones, and mike, How can I connect them?

 

I would like to be able to mix and match components but can't figure wiring diagram.

 

plugsil3.th.jpg

 

Thanks.

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How sure are you the large plug is speakers only? I thought that also but found on mine the 2 contacts on the large plug are the mic, and 2 of the contacts on the small plug are speakers with the remaining being PTT.

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On vast majority of FRS and Ham radios the PTT works by connecting a 1k to 4k ohm resistor from the Mic line to ground. Meaning there is no separate PTT signal going into the radio.

 

I do not know the pinout of the Midland headset connector, but a quick Google search came up with this:

Midland mic/spkr circuit

 

Did the "helmet kit" you are using come with the radio?

 

--

Mikko

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Interesting. How does that diagram trigger to the PTT?

I read that on the Voice II systems w/ the Midland GXT series...it uses the PTT from the Voice II, *AND* the VOX on the Midland side.

 

I have an LXT...w/ the 2 pins, trying to figure out how to connect to an Autocom.

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Like I said, I don't know about those crazy Midland radios... grin.gif

 

But looking at the drawing at bottom left. In that circuit the PTT signal (pin 5 at the intercom connector) goes to GND when you transmit. That closes the circuit on the relay coil, and relay connects the mic signal from the bottom audio isolator into the radio. Also, in parallel with the isolator, you see the 1K resistor.

THAT resistor (from mic input to mic GND) is what keys the radio.

 

Without the resistor when the relay pulls, mic signal would go into radio but radio would not switch to TX mode.

 

In Autocom 5-pin DIN connector (radio jack, not headset) pin 5 (looking INTO the DIN jack, the pin at 4 a clock) is PTT.

That pin connects to GND when Autocom wants to transmit.

You connect (looks like a 1K in case of Midland, I dunno) a resistor from that pin to mic input of the radio.

 

--

Mikko

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Charles Elms

How sure are you the large plug is speakers only?

 

When I plug a standard "large plug" stereo earphone into the radio, I get mono from left ear piece. The jack on the radio also says "SKPK" . The smaller jack says "MIC/CHG". I was also misreading my meter.

 

When it is set on the 20K ohms range it reads 1.26 with PTT open to .8 PTT closed. That's from the tip to the base, skipping the middle contact.

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We have the Midland gxt850's. Since we also run mp3 players, we run them through Starcom1s. Similarly we are interested to go to ear plug speakers. Starcom offers them for $108 a pair with a microphone, or $54 without.

 

Still I had been thinking of maybe trying to get away from Starcom's PTT button. We seem to get long delays after one of us talks before the other can be heard, and I think its in the Starcoms (radios seem to work perfectly handheld, starcom interupts music channel for radio, and also even though VOX is off, it may still be having some effect). They wire the PTT into their unit, then out to the radio. I had been thinking I could get the Midland set with the speakers and mic you've got, and try to wire that into the Starcom.

 

Well, I was only just starting to think about this when this thread came up, need to write starcom first. But I'll be watching this thread.

 

lurker.giflurker.giflurker.giflurker.gif

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Charles Elms

What started this was that I listen to music when I ride through the stock speakers. With A Cee Baileys Shield it's possible at 70-75 mph. Maybe not Norah Jones, but definitely Beach Boys. thumbsup.gif I then got the Midland to have bike to bike. It works ok with the helmet kit. PTT is fairly large and boom mike is ok, but I would like to go to something like Arizona Al's earplugs with speakers. That would mean that I need to get bike to bike working with separate audio circuit and wiring from the helmet wiring. I don't need a mixer, I would listen to MP3 player directly when not connected to bike to bike.

 

The radios came with small ear bud, boom mike, and PTT all on plug shown on first post. I broke off the large plug that is for the speaker. I can now get a separate audio from the unit. What I want to do now, it to replace the PTT switch and leave the existing mike alone. Thus the threads on the PTT.

 

As I work this out, I will keep you posted.

 

Thanks for the input.

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Interesting. How does that diagram trigger to the PTT?

I read that on the Voice II systems w/ the Midland GXT series...it uses the PTT from the Voice II, *AND* the VOX on the Midland side.

 

I have an LXT...w/ the 2 pins, trying to figure out how to connect to an Autocom.

Woodie,

I will be at work in the afternoon. I can bring my radio to show you and test with your setup as well. Let me know.

 

a

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What started this was that I listen to music when I ride through the stock speakers

 

By this you mean a BMW music system with dash mounted speakers? Won't the ear plugs adversely affect this?

 

I had heard of Az Al's. I couldn't remember which member it was. I'll go look them up.

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Charles Elms

Quote:

What started this was that I listen to music when I ride through the stock speakers

 

 

 

By this you mean a BMW music system with dash mounted speakers? Won't the ear plugs adversely affect this?

 

I had heard of Az Al's. I couldn't remember which member it was. I'll go look them up.

 

Stock BMW radio setup. Even though I've enjoyed over 50,000 miles of music through speakers, I've decided to use custom earplug speakers. I'll just plug them into my MP3 player for music when I tour and plug them into my Midland FRS/GMRS when I want bike to bike. For now, those are exclusive options. Most of my riding is solo so I don't need bike to bike. Plan to take several long trips with a friend and would like to have bike to bike.

 

After I get custom ear phones, my stock radio and speakes will not be used. I will remove radio to make room for other 'good' stuff.

 

Maybe an autocom later. wink.gif

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John Bentall

My solution for my old R1100RT involved an Autocom - buy a pre-owned Active 7 Smart or Pro-M1 or M7 to save money.

MP3 into radio-cassette slot via a cassette adapter. Radio into Autocom. Autocom cable 1187 containing 3.5mm jack plug for in-ear speakers.

Autocom should be able to provide an adapter for the Midland radio.

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Charles Elms

Here is what I've found so far. Large diameter 2-contact plug is definitely speaker.

Small diameter 3-contact plug is for the mike. Only two of the three contacts are used. I can't get into the plug, but there are only two wires coming from it.

The PTT switch just connects a 1000 ohm resistor across the two mike wires when pressed. I may be wrong on the value of the small resistor, but it reads 2.2 on the 20K ohm scale.

 

I totally destroyed one of the two supplied, small-ear-piece boom-mike and PTT units that came with the radio. Don't know why they used a three connector plug for the mike as only two wires come from it. Damn those wires are thin. Had to use a magnifying glass to see this stuff. Can't be old eyes blush.gif

 

I'm going to buy a replacement three pin mini plug and see if I can wire in my own noise canceling mike and PTT switch.

 

Results at 10.

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I sent an email to Midland, and they responded with two wiring diagrams!

 

The PTT is funky, because there is indeed a resistor there. Also, fyi, the LXT3xx series GMRS radios will work with an Autocom, using the Cobra/Uniden 2-pin connector.

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