A little project of mine involving headsets and cell phones

[Aquarius]

I had an idea recently. It sounds cool, but I need you guys' advice as to whether or not it is feasible, plus I have a couple of questions.

In one sentence, I want to find a way to hook up one of our headsets from the theatre to my cell phone so that the mic and earphone works and everything. Now for the specifics: Our headsets at school are of either this variety: Telex Intercom Headsets PH-88: Single-Sided Headset with Flexible Dynamic Boom Mic & A4F Connector

or this variety: Telex Intercom Headsets PH-88R: Single-Sided Headset with Flexible Dynamic Boom Mic & A4M Connector

First off, can anyone tell me the difference between A4F and A4M connectors?
EDIT: I looked it up, and I'm pretty sure that the only difference is that the A4F has female connectors, and that the A4M has male on the headset. In this case, our school has the A4F ones (the first link).


Now that that problem's out of the way, can anyone provide the wiring diagram for a female A4F? i.e. If I'm holding it in my hand and looking at it, which one is the headphone, ground, mic, etc.?

The jack on my cell phone (LG Dare, btw) is capable of stereo audio and microphone at the same time. It is a female standard 3.5mm jack, so I would need a male connector. I know the wiring for 3 pole 3.5 mms (tip is left earphone, middle is right, top is ground), but I am unfamiliar with the 4 pole ones. I found this link: Zen Vision :M Video Cable & Other 4-Pole 3.5mm Pinouts

which kind of helps, but I need the pinouts for microphones, not video cable. Basically, I'm trying to trick the phone into thinking that one of these is plugged in:

Phone headset

and to do that, I need to find the pinout for that type of device. Although I believe that one of the "pins" will be left blank, because our headsets are mono, not stereo.



Well, that's my story. Does it seem workable? Ask if anything's unclear.

Thanks in advance for answering my questions

 

[avkid]

Ask if anything's unclear.

Thanks in advance for answering my questions

My only question is why?

 

[Aquarius]

So that I can walk around with a tech headset plugged into my cell phone and talk on it!

Also, so that I can listen to music from my phone through a tech headset whilst working.


Just because it would be cool!

 

[dramatech]

most all tech headsets use a dynamic microphone, and the jacks on cellphones require an elctret condenser microphone. There are plenty of telephone compatible headsets available that are much more comfortable and far less expensive than tech type headsets. Try mpja.com or allelectronics.com. Being surplus sales they will have different models at different times, but a headset compatible with your phone will cost about the same or less than the connectors needed to make an adaptor for your tech type headset.

 

[NickJones]

I used to have a setup like this for recording prank calls. The speaker output of my mobile could go into the computer, and I had another Mic for recording what I said. It was wonderful to be able to phone someone from school, record it and then spread it round on my 16mb usb. Ah the joy of making someone you hardly know hit themselves in the crotch with a Nintendo 64....
Nick

 

[Aquarius]

most all tech headsets use a dynamic microphone, and the jacks on cellphones require an elctret condenser microphone. There are plenty of telephone compatible headsets available that are much more comfortable and far less expensive than tech type headsets. Try mpja.com or allelectronics.com. Being surplus sales they will have different models at different times, but a headset compatible with your phone will cost about the same or less than the connectors needed to make an adaptor for your tech type headset.

So are you saying that the two types can't work together?

Or just that it would be un-economical (is that a word?)...

Because if it's the latter, that doesn't bother me. I'm just wondering if this will work without destroying the headset and/or cell phone.

 

[gafftapegreenia]

I don't like people using headphones to listen to music while working, a technician needs to be aware.

 

[Aquarius]

I don't like people using headphones to listen to music while working, a technician needs to be aware.

Of course I wouldn't use it while running a show or doing other concentration-intensive stuff. Then the headset would be plugged into the belt pack. It'd just be for the down time when I have nothing better to do.

Also, this project is partially to gain more experience with making connectors and soldering, as we are going to be installing more speakers soon and those are going to need cable and different inputs and such...

Can it be done?

 

[Amiers]

So that I can walk around with a tech headset plugged into my cell phone and talk on it!

Also, so that I can listen to music from my phone through a tech headset whilst working.


Just because it would be cool!

Not only is it silly but potentially dangerous you could miss a cue or be standing somewhere you shouldnt and get hit by soemthing.

The other problem with this is I dont believe there is a way to connect ones phone to any wireless station out that I know of ATM.

 

[Aquarius]

My apologies for giving the idea that I would wear it whilst working.

A lot of you have commented on its impracticality. That's all good and fine (or something like that). This is more of a "I'm doing it because I can" project than an "I'm doing it because it's useful" project.

 

[dramatech]

In the case of trying to use dynamic mics on circuits designed for electret mics only, they don't work. The opposite is also true, that electret mics don't work on dynamic circuits.
It is possible that you might hear something through the mic used in the wrong circuit, but it will be very faint and distorted.
I have done the opposite of what you are trying several times. I wanted to use the very inexpensive headsets, made for computers and cellpnones, on intercom beltpacks. The reason is because they are much lighter and, at the rate that our crew can destroy heasdets, it is just simple math when it comes to the dollar. I have succeeded in modifying beltpacks to use electret mics, but it is a bit of work.

 

[Aquarius]

Dang. Would the earpiece work?

 

[dramatech]

yes the earpiece would work!!

 

[derekleffew]

On the Telex headset referenced above, the Mic Impedance is 200Ω and the Speaker Impedance is 300Ω. What are the respective impedances of your cell phone?

 

[Aquarius]

I believe that the max is about 20Ω for speakers.

I see the problem. The phone doesn't put out enough juice to power the headset. Gotcha.

 

[epimetheus]

I believe that the max is about 20Ω for speakers.

I see the problem. The phone doesn't put out enough juice to power the headset. Gotcha.

Actually it requires more "juice" to drive a 20 ohm load than it does to drive a 300 ohm load. I'm only commenting about the speakers since it's already been covered that the mics are incompatible without modifications.

 

[Chris15]

A dynamic mic will work in place of an electret. The dynamic is likely to need more gain but fundamentally you are inputting an AC waveform to something expecting... an AC waveform.

Likewise the only change needed to use an electret is to add bias power...

Now, putting aside the question of why, who owns the headset?

Given you are talking about using this as a project in building up your soldering skills, if you mess it up and short something and it kills your phone, well that's your loss. If it takes down a school headset is that going to cause you issues?

Those disclaimers aside, There is not yet a proper standard on 4 pin 3.5mm wiring. Most people however are using tip left, ring 1 right, ring 2 "other" signal and sleeve ground. Doing so means that you can plug standard headphones in and have them work...

Assuming we get over the level mismatch of mics, XLR pins: 1 mic ground, 2 mic, 3 & 4 ear. So assuming the aforementioned 3.5 wiring, tip - pin 4, ring 1 N/C, ring 2 - pin 2, sleeve - 1 & 3. (Pins 3 & 4 are reversible).

 

[Aquarius]

A dynamic mic will work in place of an electret. The dynamic is likely to need more gain but fundamentally you are inputting an AC waveform to something expecting... an AC waveform.

If I'm reading this correctly, this means that I would need to talk extra loud into the headset to be able to be heard, or change the mic level setting on my phone. Is this correct?

Likewise the only change needed to use an electret is to add bias power...

Huh?

Now, putting aside the question of why, who owns the headset?

Given you are talking about using this as a project in building up your soldering skills, if you mess it up and short something and it kills your phone, well that's your loss. If it takes down a school headset is that going to cause you issues?

No problem here. I found some old headsets that still work, but we don't use, up in the catwalk storage. The TD said I could use these for whatever I wanted, as otherwise they were going to get thrown out.

Those disclaimers aside, There is not yet a proper standard on 4 pin 3.5mm wiring. Most people however are using tip left, ring 1 right, ring 2 "other" signal and sleeve ground. Doing so means that you can plug standard headphones in and have them work...

THANK YOU!

Assuming we get over the level mismatch of mics, XLR pins: 1 mic ground, 2 mic, 3 & 4 ear. So assuming the aforementioned 3.5 wiring, tip - pin 4, ring 1 N/C, ring 2 - pin 2, sleeve - 1 & 3. (Pins 3 & 4 are reversible).

Thank you again for providing this! Now I just need to get out and buy the materials, I guess.

It was mentioned before that it takes less energy to power a 200 ohm earpiece than it does a 20 ohm. Therefore, if my phone can take a max impedance of 20 ohms, it should be able to power the earpiece. Correct?

 

[Chris15]

If I'm reading this correctly, this means that I would need to talk extra loud into the headset to be able to be heard, or change the mic level setting on my phone. Is this correct?

Maybe... There may also be some impedance problems. We may also be talking about an increased gain outside the range of what your phone can cope with...

Huh?

It does not apply to what you are doing, ignore it. It was intended in relation to previous discussion...

It was mentioned before that it takes less energy to power a 200 ohm earpiece than it does a 20 ohm. Therefore, if my phone can take a max impedance of 20 ohms, it should be able to power the earpiece. Correct?

I guess one could say just try it.
As a quick test, you could grab a 3.5mm to bare ends and piggy back them on the back of the XLR to check things...