How attach external recording lead to answering machine?
Johnno
telephone answering machine. Thanks in advance for any help.
I want to archive some messages from my answering machine. The
answering machine is built into a DECT cordless phone which is one of
the PANASONIC KX-TG7100 range. My phone <http://tinyurl.com/kmg6vb>
I could replay the messages with a mic near the speaker but the
recording quality is poor. So I want to attach a wire to the phone
and record the audio signal on my MP3 recorder.
The phone replays messages through a speaker in its base unit or
through the earpiece on the handset. There's also a handset speaker.
What sort of circuit would I need to attach a recording lead to the
speaker contacts?
(Below are details of photos, service manual and how to identify
similar Panasonic models.)
Johnno
--------------START-OF-DETAILS--------------
PICTURES OF THE PHONE'S INTERNALS
These are photos I took of the speaker and of the contacts on the
circuit board:--
(1) handset - circuit board.jpg http://bayimg.com/bABPHAAcc
(2) handset - speaker - front.jpg http://bayimg.com/babpFaaCc
(3) handset - speaker - rear.jpg http://bayimg.com/BABpiAACc
(4) handset - speaker - side.jpg http://bayimg.com/BAbPNaACC
(5) base unit - front .jpg http://bayimg.com/babpPaACc
(6) base unit - circuit board.jpg http://bayimg.com/CabpDAacc
(7) base unit - rear.jpg http://bayimg.com/CabpfaAcC
Here is the service manual for this phone (Central European
edition):-- <http://freepdfhosting.com/cecffb76d5.pdf>
I think page 55 of the service manual is saying the handset speaker is
8 ohms; and the 2 terminals going to the speaker is 150 ohms.
---------
DECODING PANASONIC MODEL NUMBERS
I'm in the UK. My DECT phone is one of the PANASONIC KX-TG7100 range.
About a year ago the range was replaced by the Panasonic KX-TG7200 and
also by the Panasonic KX-TG7300.
Info about very similar Panasonic phones might get overlooked unless
you decode Panasonic's model numbers. For example, my specific model
is actually a Panasonic KX-TG7122ES.
NOTE:
The last zero can be "2", "3", "4" to indicate number of handsets.
The penultimate zero is set to "2" for a built-in answering machine.
Any extra suffix will indicate the country. ("E" for UK English model)
Any second extra suffix indicates colour. ("S" for silver, etc)
--------------END-OF-DETAILS--------------
William Sommerwerck
choice. You don't need to rewire anything. Just lay it over the speaker.
If the hand unit has an earphone jack, you could use that. You'll have to
modify a headset cable, as I doubt anyone makes a headset cable with jacks
where the headset would be.
Graham.
"Johnno" <joh...@mail.invalid> wrote in message
news:Xns9C2E696...@newsfarm.iad.highwinds-media.com...
Do you think you could solder two short wires to the speaker terminals?
route them through the battery aperture and re-assemble the phone.
Now find an lead with a 3.5mm jack-plug on one end, perhaps
cut off an old pair of earphones etc. but note that the wires in
the thin cables with some "in ear" types are extremely
difficult to work with.
Now just connect the "tip" and "sleeve" of the jack lead two the wires
coming out of your phone if your jack-lead is stereo it will have a
third "ring" contact just ignore it.
Plug it into the MP3 recorder.
It might be better to use a computer with a sound application. Use "Line In"
If you find the results are too loud and distorted you need to adjust
with the speaker volume on the handset and/or the line in gain
on the recorder. If you are using the computer, mute all the unused
inputs in the volume control applets especially any built-
in microphone in a laptop.
--
Graham.
%Profound_observation%
Johnno
Thank you for your reply. I would GUESS the DECT phone's speaker output
on the base or the handset is something like 250 mW (not mV). That would
probably overload a line input and would most definitely be a problem for
a mic input.
I'm sure that if I use an un-isolated connection as you describe then
there might be nasty earth-loop hum and other noises, especially if the
signal is fed into a PC!
I'm not at all sure if there's a neat way to isolate the feed while at
the same time as attenuating it's signal level. Maybe someone will
advise.
Just putting in some dropping resistors could mess up the frequency
response quite a lot by mismatching various impedances. I'm not at all
sure how to deal with the 150 ohm circuit shown the handset speaker
circuit. One alternative might be to use the handset earpiece (not
speaker) but I've no idea what sort of impedance would be presented to
the earpiece transducer (which might be piezo).
William Sommerwerck
Problem solved.
Johnno
Thanks for the info.
I already tried one of those pickup coils but the signal is extremely
weak and noisy. The result is less good than using a mic near the
speaker.
I've heard others people say they get reasonable results (on modern
phones rather than old ones with larger inductors). Unfortunately I've
never got anything like that from these pickup coils.
Perhaps they come in different sensitivities although I doubt it.
Graham.
Johnno, I know it's not an elegant solution from an impendence matching
standpoint etc. but I know from experience it should work with little or no
perceivable loss in quality.
Earth loop is not an issue here because at least one end of
the interconnect is floating, wireless in fact.
Even if there is a speaker in the base unit, (there seems to be one,
but it might just be a ringer) this too will be isolated from earth
by the wall-wart *but* disconnect the phone line-cord while
you have any of your stuff connected to it.
Because of this isolation I did not even specify the "tip" of the
jack to go to the red lead of the speaker etc. It will
make no difference if you reversed them.
If the mV level from the speaker overloads the line in you
will naturally turn down the speaker volume, I doubt if
you will need a pot in the lead.
--
Graham.
%Profound_observation%
Jono
> Can you specialists help me attach a lead to record messages from my
> telephone answering machine. Thanks in advance for any help.
Can you remotely interrogate your answerphone?
If I needed to do what you're doing, I'd call in from work (where calls
are recorded), listen to my answerphone messages and archive the
recording from the office system.
Some mobile phones allow you to record the call and save the resultant
file to a memory stick.
Johnno
Graham, thanks for info. Can you or anyone else help me work thru the
situation? I need to be sure of things because the archived recordings
may be played to third parties as a form of proof ---------
The base unit and handset each have a speaker for audio which also
double as ringers. The info in the service manual confirms this.
All speaker contacts are internal so there is no danger of human
contact. It therefore seems possible that the base unit speaker could
have one terminal wired to the incoming power supply and therefore
might be grounded???
On account of this, presumably it is better to attach my new recording
line to the handset and not the base unit. However the handset is
connected via a radio link. Would this normally be sufficient to
preserve audio quality such that the handset audio when playing
messages is as good as the base unit's audio quality?
If I am going to use the handset for the line tap then I'm inclined to
use the eariece rather than the speaker. This is because the speaker
needs more amplification which I would then need to reduce by
attenuating it. Apart from squelching the spoken audio in a phone
call, the audio from the handset speaker seems to have had some
processing applied to it: in a phone call there is very effective
removal of echo and boominess. In addition the speaker seems to have
a "bigger" sound as if there is SRS's WOW or some sort of audio
manipulation like it. I wouldn't really want any of that on a
recording.
If I have to use the handset's earpiece then it seems the transducer
might have an impedance of several hundred ohms (compared to the 8 ohm
empedance of the speaker).
Surely it's worth trying to mesh with this? Epanorama says the
impedance of a PC soundcard is approx 1,500 to 20,000 ohms
http://www.epanorama.net/links/pc_sound.html. A mic jack socket on an
MP3 recorder is about 2,000 ohms. I don't have a line input on a
recorder.
Is my line of thinking reasonably correct?
captainvi...@yahoo.com
> MP3 recorder is about 2,000 ohms. I don't have a line input on a
> recorder.
>
>
> - Show quoted text -
It sounds like you have a good sense of basic electronics. Google both
L and H pads. You can build an attenuator that will match impedances
on both input and output. I think that its an "H" pad but I'm not
sure. I don't remember my formulas . Its been a while since I've
looked at them but there are many different types of pads for many
applications and each pad has its own formula. You can plug in Z1 and
Z2 and your desired attenuation regardless of operating frequency, (to
a large extent), and for example with the H pad by employing a network
of three resistors you will match input to output impedance and
provide the desired attenuation as well. If I can find my formular
sheet I'll post it. Good luck. Lenny
b
> Can you specialists help me attach a lead to record messages from my
> telephone answering machine. Thanks in advance for any help.
I think you're in danger of using a sledgehammer to crack a nut here.
We're talking about ultra lo-fi speech on equipment with a frequency
response of about 5khz tops.
I would just mike it up (a hi fi cassette deck would prbably be better
than an mp3 recorder), record it and use that copy. Transfer to PC if
needed via line in.
I have done this in the past several times .You just have to watch
your volume on the handset so it does not distort the little speaker,
or make the plastic vibrate etc. And use a good mic.
-B
Bob Larter
> If I have to use the handset's earpiece then it seems the transducer
> might have an impedance of several hundred ohms (compared to the 8 ohm
> empedance of the speaker).
>
> Surely it's worth trying to mesh with this? Epanorama says the
> impedance of a PC soundcard is approx 1,500 to 20,000 ohms
> http://www.epanorama.net/links/pc_sound.html. A mic jack socket on an
> MP3 recorder is about 2,000 ohms. I don't have a line input on a
> recorder.
If you have to use a mic input, then you'll need to attenuate the signal
from the speaker terminals. I'd try attaching a 1K pot across the
speaker terminals & picking up the signal off the wiper.
--
W
. | ,. w , "Some people are alive only because
\|/ \|/ it is illegal to kill them." Perna condita delenda est
---^----^---------------------------------------------------------------
James Sweet
>
> Thank you for your reply. I would GUESS the DECT phone's speaker output
> on the base or the handset is something like 250 mW (not mV). That would
> probably overload a line input and would most definitely be a problem for
> a mic input.
>
> I'm sure that if I use an un-isolated connection as you describe then
> there might be nasty earth-loop hum and other noises, especially if the
> signal is fed into a PC!
>
> I'm not at all sure if there's a neat way to isolate the feed while at
> the same time as attenuating it's signal level. Maybe someone will
> advise.
>
> Just putting in some dropping resistors could mess up the frequency
> response quite a lot by mismatching various impedances. I'm not at all
> sure how to deal with the 150 ohm circuit shown the handset speaker
> circuit. One alternative might be to use the handset earpiece (not
> speaker) but I've no idea what sort of impedance would be presented to
> the earpiece transducer (which might be piezo).
You need an attenuator to connect the speaker output to a mic input.
This is nothing more than a couple of resistors, usually one fixed and
one variable. Some experimentation will find something that works well,
it's really not very critical, especially for the low quality sound from
an answering machine. You likely won't have any problems with ground
loops and hum.
David Woolley
> Go to your nearest RatShack. Buy one of these for $8
Problem with that is the cost of the air fare, and the time you have to
take off for the visa interview.
This is cross-posted to UK.telecom and Radio Shack (they branded
themselves as Tandy) sold out to a mobile phone retailer many years ago
here. I don't believe that Maplin, the nearest equivalent, does phone
pickup coils.
>
Bob Eager
Maplin LB92A, £4.99....
--
Bob Eager
Use the BIG mirror service in the UK:
http://www.mirrorservice.org
Sofa Slug
Go to: http://texatone.com/pages/Attenuators/Basics.html
The info presented is geared towards guitar amps, but the basic
principles will apply.
Scroll down the page about 1/2 way & click on the "Here are the diagrams
for the following descriptions:" link. At the bottom of the page you
will see schematic diagrams for what you are trying to do.
David Nebenzahl
> Can you specialists help me attach a lead to record messages from my
> telephone answering machine. Thanks in advance for any help.
>
> I want to archive some messages from my answering machine. The
> answering machine is built into a DECT cordless phone which is one of
> the PANASONIC KX-TG7100 range. My phone <http://tinyurl.com/kmg6vb>
>
> I could replay the messages with a mic near the speaker but the
> recording quality is poor. So I want to attach a wire to the phone
> and record the audio signal on my MP3 recorder.
Here's my $0.09 (adjusted for inflation). Some time ago I had some
interesting answering machine messages I wanted to save, and I tried
connecting the machine directly to a recorder (cassette). I found a
place that gave me a signal on the machine (equivalent to line out), but
the results were pretty horrible; very muddy sounding, as it seemed like
anything over about 1 kHz was practically cut off. (Could have been an
impedance mismatch problem, I suppose, but I suspect it's really because
the answering machine is such a lo-fi device.)
I ended up just recording them using a microphone and cassette recorder,
and got much better results. Don't bother dicking around trying to
connect it directly is my advice.
--
Found--the gene that causes belief in genetic determinism
Sofa Slug
A variation of this idea would be to install software on your computer
to record from the phone line (your PC must have an internal/external
modem): http://www.allformp3.com/record-phone-conversation.htm
After installing the software, call your home phone from your cell. When
your answering machine picks up, enter your ID code to play back your
messages. Record them on the PC.
Proteus IIV
BUY A BETTER ANSWERING MACHINE
I AM PROTEUS
Johnno
> orama.net/links/pc_sound.html. �A mic jack socket on an
>> MP3 recorder is about 2,000 ohms. I don't have a line input on a
>> recorder.
>>
>> Is my line of thinking reasonably correct?- Hide quoted text -
>>
>> - Show quoted text -
>
> It sounds like you have a good sense of basic electronics. Google
> both L and H pads. You can build an attenuator that will match
> impedances on both input and output. I think that its an "H" pad but
> I'm not sure. I don't remember my formulas . Its been a while since
> I've looked at them but there are many different types of pads for
> many applications and each pad has its own formula. You can plug in
> Z1 and Z2 and your desired attenuation regardless of operating
> frequency, (to a large extent), and for example with the H pad by
> employing a network of three resistors you will match input to
> output impedance and provide the desired attenuation as well. If I
> can find my formular sheet I'll post it. Good luck. Lenny
Thank you for the info.
Johnno
Nice link. It's very close to what I want to do. I'll give their
circuit a go.