Maybe, but the termainl board certainly seems to melt very easily. Oh, I managed to extract the intenrals from the box, But the box still contained quite a bit of gunge (not a problem, I could scrape that out, and I can also heat the box, being a metal can, to quite a high temperature without problems) and of course there's similar potting compound on the intenrals. I don't want to get those too hot for risk of damaging them. I can indentify the expected ocmponents in there -- (2 varistors that look like disks with metal coating on the surfaces), the anti-sidetone transformer ('induction coil'. call it what you like :-)), some normal-looking resisotrrs, and a stack of 2 capacitors in a clip holder thing. But with the gunge all overe them it's not easy to work on. -tony

In telephony, 'sidetone' means the signal in your receiver due to thr signal from your transmitter. If you are not careful, the sounds you hear the other hand, if there is no sidetone, the user is inclined to shout. If you subtact your locally-generated signal from the signal on the line (which, of course, ilncludes said local signal), you end up with only the signal from the other telepghone. If you do it perfectly, yuou have no didetone at all, by varying the rations you can get jsut enough sidetone to make the telephone easy to use. There are many ways of doing this subtaction. The older modems I work on tend to use a couple of op-amps. Modernt landline telephones often use a disctrete transistor circuit(2 or 3 transistors [1]). Older telephones both in the UK and US (and I assume elsewhere) use an audio transformer, often called (at least in the UK), the 'induction coil'. There is such a transformer in the 'Network' block I metnioned. [1] The cheap telephone I bought from Maplin to use with my line simulator uses 3 bipoloar transistors for this. You could also look at the manual for the Elenco telepohone kit (available on their website) to see a 2 transistor circuit. -tony

Sam Hallas's web site (I forget the URL, but Google should find it) has some exceleltn information on this. This site has most of the 'N Diagrams' avaialbe to download (the N diagrams are essentailly the scheamtics of various telephones, bells, extension plans, etc that were used by the British Post Office) -- in fact a Google search for 'N diagram' is probably the easiset way to find it. It also has some educational maaterial used to train the Post Office telepghone engineers, including an excellent (and very clear) deascription of the 700 series phones including the hybrid and regualtor circuits. -tony

At 03:52 PM 3/29/2011, Alexandre Souza - Listas wrote: I remember encountering it when I was kid, in a similar phone. Impossibly sticky. Probably full of PCBs or something. - John

One of your roomies leaves circuit boards on your chair and you get excited over a ceramic 1980 8742 with eprom window on it and a AM2864 ceramic eeprom. (84 datecode)

Yes they were socketed, was part of some sort of access intercom system from an old apartment bldg. they upgraded them to a digital access system. Even if they weren't, I have a HAKKO808 desoldering gun and am damn good at desoldering with it :) On 3/30/11 7:31 PM, "Dave McGuire" <mcguire at neurotica.com> wrote:

On 3/30/11 10:59 PM, "Wolfgang Eichberger" <oe5ewl at gmail.com> wrote: My lady is just glad that I've gone from keeping boxes of old PC Boards, to pulling the useful parts off them and recycling the rest.

Given that there is no standard European netowrk, I am not sure quite wwhat this is saying. Yes, thankfully. I think I have 4 American telepghones. A WE/Bell 500 (rotary dail, with this potted network block) A WE/Bell 564 (rotary dial, 5 line select buttons, again with the network block. No I don't have a relay set for it) A AE/GTE rotary dial telephone/ There's a PCB in the bottom carrying the hybrid netowrk components and the hookswitch. A 2500 DTMF set made by one of the ITT-related companies. This has a smaller PCB (about the size of the network block in a WE phone) carrying the hybrid network componetns/ The hookswtich is separately mounted to the baseplate. This one has the rather odd 'chuttling ball' ringer. Alas it ahs the modern DTMF dialer with an IC on it (it's a 5089 or similar, I am sure). Needless to say the PCBs don;t pose any real problems. Incidentally, if anoy needs information on such telephoens, I've found the sties http://www.telephonecollectors.info/ and http://www.telephonetribute.com/ are worth looking at. Tha'ts the stuff alright ;-(. I fon't remember any smell though. Yes, I gound out that soap and water was no good when I got it all over my hands... I am suprised the formula was so secret, given that the scheamtics, etc exist. Interesting. I am suprised the solvents I tried didn't appear to have much effect. However, I may well try putting the module and can in some white spirit (about the cheapest of those solvents) and leaving it. Yes, I discovereth that the hard way ;-) I think some of the mdoern ones are even hardter to remove without damaing the internals... -tony

On Thursday (03/31/2011 at 08:10PM +0100), Tony Duell wrote: Maybe it's Gutta-percha, http://en.wikipedia.org/wiki/Gutta-percha It was popular with the telephone (cable) crowd at least ;-) -- Chris Elmquist

On 3/31/2011 4:11 PM, David Griffith wrote: I recall what you all are talking about, and it reminds me of the silicon glue type stuff, minus the vinegar smell that the early versions of that we got had. Never thought about it other than the fact that both were soft at room temp, and had about the same diluted milky quality color. If the temperature is an issue above water boiling point, one could use hot oil to supply the temp, but it would still have a lot of heat, which could damage it. Jim

---snip--- ---snip--- Peanut oil is the best for heating things. I is good for temperatures hot enough to melt solder. As for fires, always have a cover large enough for the container. Just put the cover over the fire. Dwight

On 2 Apr 2011 at 19:22, Tony Duell wrote: be). You're welcome. --Chuck

Thank you for that link. I'd not come across that company before, and while their prices for complete phones are rahter too high for me. they have lots of spares at affordable prices which will be useful. One annoying thing is that, in common with just aobut all other old telephone sellers, they say much mroe about the outsides than the internals. I would love to get a DTMF phone with the origianl 1-tranistor,no ICs encoder (the one wit hthe 2 pot cores on the back). Needless to say I don't care what colour or style the phone is, my interest is in the circuirty, But I've yet to find a phone listed anywhere where that sort of thing is specified. Hwoever, getting back to this 'Network' since when have I been known to replace something if there's any chance I could repair it :-) -tony

I forgot to mention the obvious physicl property -- the colour. It's almost transparent (slightly milky/translucent). Pitch is surely opaque black. Also, it does not disolve in any common solvents (so far I've tried propan-2-ol, metylated spirits, petrol, white spirt and a couple of different paint thinners). It is very sticky at room temperature. it's not really hard. -tony

My experience is that it's a lot easier to remove soft potting compouds without damaging the stuff inside than hard ones. I don't think cooling it will ehlp -tony