Eric Prebys <pre…@viper.princeton.edu> wrote:
>OK, admittedly I’m being a cheapskate, but I was trying to adapt
>a standard telephone headset for use in a airplane. The headphone
>part of course works fine, but after finding the elusive
>.206" plug to connect the microphone, it still does not work.
>Does anyone know if there is a fundamental difference between the
>microphone types? Also, I noticed there were three contacts
>on the mic plug. I assumed that two were for the mic and
>the third was for a remote ptt button. Do aircraft headsets perhaps
>use a powered mic?
Well, I must be a cheapskate too, because I did the same thing
(successfully). First off, the headphones may seem to work, but the
aviation headsets have a much higher impedance than the hi-fi
variety. Some intercoms can’t drive that low impedance, and they
load down the output so much that the other headphones (my
instructor’s, in this case) are almost impossible to hear. When I
discovered this, I attached a small impedance-matching audio
transformer to the side of one of the ear cups (looks a bit
Frankensteinish). As for the microphone, aviation mics are designed
to emulate a carbon mic. That is, they present a variable
resistance to a current flow driven by +12 volts. I was able to rig
up an electret mic to the base of a transistor, and by playing
around with the emitter resistor and collector resistor, I got
something that ATC could hear. It was not good quality, though, and
I now use Marv Golden’s $89.95 marvel. You’re right about the PTT
switch. It switches to ground.
-Bob Scott
OK, admittedly I’m being a cheapskate, but I was trying to adapt
a standard telephone headset for use in a airplane. The headphone
part of course works fine, but after finding the elusive
.206" plug to connect the microphone, it still does not work.
Does anyone know if there is a fundamental difference between the
microphone types? Also, I noticed there were three contacts
on the mic plug. I assumed that two were for the mic and
the third was for a remote ptt button. Do aircraft headsets perhaps
use a powered mic?
I’d appreciate any information.
-Thanks,
Eric
In article <31E2C8F8.1…@viper.princeton.edu>,
Eric Prebys <pre…@viper.princeton.edu> wrote:
>Does anyone know if there is a fundamental difference between the
>microphone types?
Well, for starters, telephony uses 48 volts for conversation. Your aircraft
system isn’t going to drive that microphone.
>Also, I noticed there were three contacts
>on the mic plug. I assumed that two were for the mic and
>the third was for a remote ptt button. Do aircraft headsets perhaps
>use a powered mic?
No. Your original assumption was correct. The tip is used for the PTT.
———————————————————————–
| I pity the man who don’t drink, ’cause when he
George Patterson – | gets up in the morning, that’s as good as he’s
| going to feel the whole day.
| Joe E. Brown
———————————————————————–
In article <31E2C8F8.1…@viper.princeton.edu>, pre…@viper.princeton.edu says…
>OK, admittedly I’m being a cheapskate, but I was trying to adapt
>a standard telephone headset for use in a airplane…………..
Go get him, Jim!
(LOVE my RST headsets, intercom, etc.)
Dave Musgrave
Eric Prebys wrote:
> Does anyone know if there is a fundamental difference between the
> microphone types? Also, I noticed there were three contacts
> on the mic plug. I assumed that two were for the mic and
> the third was for a remote ptt button. Do aircraft headsets perhaps
> use a powered mic?
> I’d appreciate any information.
> -Thanks,
> Eric
I have a related question. Has anybody tried connecting the
line-input of a video camcorder to the intercom? I would
assume that line is probably a high-impedance input (470k
to 1Meg) and that the intercom expects to see around 600ohms.
Anybody has experiences with rigging a camcorder to the
intercom and recording the ATC and internal aircraft
conversation? Thanks.
Sriram
Pleasanton, CA
PP-ASEL
Connecting a high impedance device to a low impedance output port will
not usually cause a problem, unless the port counts on the current
demand of the load for operation. That is very rare in modern equipment
design. Usually it just means that you a taking a small current from a
device that could supply more. However, connecting a low impedance
device to a high impedance output will usually not work very well. Once
again, with modern equipment you will probably not damage anything. You
just won’t get anything either. Ideally, for maximum efficiency in the
transfer you would want both devices to have the SAME impedance.
High impedance devices are a bit more prone to picking up stray noise
than low impedance devices are.
John
- Hide quoted text — Show quoted text -
On Wed, 10 Jul 1996, Sriram Narayan wrote:
> Eric Prebys wrote:
> > Does anyone know if there is a fundamental difference between the
> > microphone types? Also, I noticed there were three contacts
> > on the mic plug. I assumed that two were for the mic and
> > the third was for a remote ptt button. Do aircraft headsets perhaps
> > use a powered mic?
> > I’d appreciate any information.
> > -Thanks,
> > Eric
> I have a related question. Has anybody tried connecting the
> line-input of a video camcorder to the intercom? I would
> assume that line is probably a high-impedance input (470k
> to 1Meg) and that the intercom expects to see around 600ohms.
> Anybody has experiences with rigging a camcorder to the
> intercom and recording the ATC and internal aircraft
> conversation? Thanks.
> Sriram
> Pleasanton, CA
> PP-ASEL
John R. Johnson wrote:
> Connecting a high impedance device to a low impedance output port will
> not usually cause a problem, unless the port counts on the current
> demand of the load for operation. That is very rare in modern equipment
> design. Usually it just means that you a taking a small current from a
> device that could supply more. However, connecting a low impedance
> device to a high impedance output will usually not work very well. Once
> again, with modern equipment you will probably not damage anything. You
> just won’t get anything either. Ideally, for maximum efficiency in the
> transfer you would want both devices to have the SAME impedance.
> High impedance devices are a bit more prone to picking up stray noise
> than low impedance devices are.
Agreed. Connecting the HiZ input to a lowZ output is likely to overload
the input stage of the HiZ device because it is probably designed to
work in the micro/milli V range of inputs rather than the milli or
volts of output a headset is designed for. There is probably not going
to be any damage, but there is likely to be unacceptable distortion and
clipping in the audio in the camcorder. A simple voltage divider may
be then an acceptable solution (even if the impedances are mismatched).
Sriram
- Hide quoted text — Show quoted text -
In article <31E40AD2.7…@corp.cirrus.com> Sriram Narayan <nara…@corp.cirrus.com> writes:
>Eric Prebys wrote:
>> Eric
>I have a related question. Has anybody tried connecting the
>line-input of a video camcorder to the intercom? I would
>assume that line is probably a high-impedance input (470k
>to 1Meg) and that the intercom expects to see around 600ohms.
>Anybody has experiences with rigging a camcorder to the
>intercom and recording the ATC and internal aircraft
>conversation? Thanks.
>Sriram
>Pleasanton, CA
>PP-ASEL
Sriram, I do this all the time. the video is complete wirh cockpit chatter and ATC. works like a charm an a number of camcorders.
–
~ bob (Bob Hutson)
==========================================================================
r…@netcom.com (408) 559-5320
Eric Prebys <pre…@viper.princeton.edu> shared the following
priceless pearls of wisdom:
->OK, admittedly I’m being a cheapskate,
I prefer to think of it as economical and a good recycler…
but I was trying to adapt
->a standard telephone headset for use in a airplane. The headphone
->part of course works fine
As well it should, being somewhere between 150 and 600 ohms as we
expect an aircraft earphone to be…
, but after finding the elusive
->.206" plug
Next time try us. We must sell ten thousand of them a year to people
doing exactly or just about what you are doing.
to connect the microphone, it still does not work.
Hmmm…it should. Do you have one of the microphone wires connected
to the ground or shell and the other one connected to the ring? The
TIP of an aircraft microphone plug is connected through a switch to
the shell; when the TIP is grounded, it places the transceiver in the
transmit mode.
->Does anyone know if there is a fundamental difference between the
->microphone types?
No there isn’t, but MAYBE you found yourself a polarized microphone.
Does it work when you reverse the leads? Telephone headsets have been
used for YEARS as emergency/cheapskate aircraft headsets.
Jim
Jim Weir VP Engineering | You bet your sweet patootie I speak for the
RST Engineering | company. If I don’t, ain’t nobody gonna.
Grass Valley CA 95945 |
http://www.rst-engr.com | AR Adv WB6BHI–FCC 1st phone—Cessna 182A N73CQ
j…@rst-engr.com | Commercial/CFI-Airplane/Glider-A&P-FAA Counselor
Sriram Narayan <nara…@corp.cirrus.com> shared the following
priceless pearls of wisdom:
->I have a related question. Has anybody tried connecting the
->line-input of a video camcorder to the intercom? I would
->assume that line is probably a high-impedance input (470k
->to 1Meg) and that the intercom expects to see around 600ohms.
->Anybody has experiences with rigging a camcorder to the
->intercom and recording the ATC and internal aircraft
->conversation? Thanks.
Well…whose intercom? Our 442 intercom comes with a line output as
standard equipment. Do you mean you want to plug the vcr into a
headphone output? Shouldn’t be much of a problem, just plug it in
directly. Or, use a Y-adapter and plug the vcr in parallel with a
pair of ‘phones so you can record and listen to what is being recorded
at the same time. We’ve done it for years making training tapes for
our stuff.
Jim
Jim Weir VP Engineering | You bet your sweet patootie I speak for the
RST Engineering | company. If I don’t, ain’t nobody gonna.
Grass Valley CA 95945 |
http://www.rst-engr.com | AR Adv WB6BHI–FCC 1st phone—Cessna 182A N73CQ
j…@rst-engr.com | Commercial/CFI-Airplane/Glider-A&P-FAA Counselor