How attach external recording lead to answering machine?

An old-fashioned induction coil (if you can find one) would be a good 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.

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.

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).

Go to your nearest RatShack. Buy one of these for $8.

Problem solved.

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.

You'll probably have to experiment. I would use the signal input to the audio power output device rather than the signal to the speaker. If you're clever enough with electronics it shouldn't be much of a problem.

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.

Johnno used his keyboard to write :

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.

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

Is my line of thinking reasonably correct?

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

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

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.

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.

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.

Maplin LB92A, £4.99....

Go to:

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.

On 6/18/2009 2:21 AM Johnno spake thus:

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.

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):

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.

BUY A BETTER ANSWERING MACHINE

I AM PROTEUS