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⬅️ Previous capture (2022-06-12)
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NOTES ON RECORDING CALLER ID signals ....(AND VOICE NOTES) There have been a number of people who have complained that caller id is not working perfectly in their area. I have been working with ZyXEL to try to get it and distinctive ring working perfectly. It now does work in most of Canada and the US. Caller id works great combined with distinctive ring. I enjoy such features as, if the modem encounters a busy bbs, it sets distinctive ring to answer a CALL return (another feature from the phone company), then answers in originate mode. Thus you can make contact with the bbs at the first opportunity after the line clears, and not have your modem be disturbed by other calls. For those (hopefully few) people who still have problems with caller-id, here is a simple way to get information to allow these problems to be resolved more quickly. In the past I circulated a circuit to do this. However, thanks to the new voice features, there is an easier way. The idea is to record the ring/callerid signalling on a voice file which can then be listened to, and uploaded to the engineers if necessary. This also allows the cadence of the distinctive ring to be measured if necessary. It is REALLY simple to do also and is fun because you can even listen to the signal and get a bit of an idea what might be wrong, even without sending in the file. It is also instructive to write a little voice display program to become more familiar with this format-- since the signals are predictable, monotonic, and thus relatively easy to analyse with a simple program. One of the problems is that some exchanges do not seem to follow the Bellcore specs for callerid. The way it is supposed to work, is that after the first complete ring (or distinctive ring) stops, there is a 500 ms pause, then a 250 ms section of "continuous" U characters sent (called a channel seizure signal), then a 150 ms section of mark sent, then the data. A simple number will take about 200 ms further. Then silence reigns until the next ring. Now the tones used are 1200 hz for the mark or 1 bit, and 2200 for the space or 0 bit. Data is sent at 1200 baud in an asychronous mode. (this is called bell 202 standard). Now the The U character is interesting in that it is 1 bit on , one bit off. Thus when it is being sent in a continuous mode, it also looks like 250 ms of the frequency shift keying signal shaped as a 600 hz square wave. What does this mean?? it means that it sounds like a quarter second of 600 hz tone. So you should hear a ring, a 1/2 second of silence, a 1/4 second of 600 hz (fundamental) tone, and then a quarter second of 1200 hz tone-- followed by a short blast of a higher note. What can go wrong?? 1st, one problem is that some switches don;t have a proper pause. you might get the U's not sent continuously which might sound like a lower note. Third the mark might not be long enough. next the frequencies may not be correct. The data can come slowly--with up to 2 characters of mark signals between data. (according to the spec). Thus you can give ZyXEL some information without sending the file. Your local exchange sends all these notes (they are not sent from long distance), so they are not attenuated very much. Please also try to find out what kind of switch the exchange has. This information can often be obtained from 611 repair service from a nice teckie. Another interesting thing is some of these switches have more than one way caller id can be sent. They may just be set to do it the non compliant way!! perhaps the technical people do not know they have a choice. Once you have the voice file, Another crude way of timing, is to use a hex editor, and lop off pieces from the end of the file (checking for the shielded code--and preserving shielded data--make sure the file is properly terminated). this way you can listen do some timing by looking a t the size of the lopped off file. You can even look at the raw data, and get the idea which area you are in. (espec in 2 bit mode). A less crude way, is to write a little program-- hey and what better way for all you folks wanting to write a voice mail system to force yourself to get started!. You can convert the voice file into one readable by some of the standard voice/oscilloscope sound blaster type programs. so you can see it on your screen. The idea is to find out what went wrong, tell ZyXEL and provide a backup recording. Now-- you may ask,, how do I get started. WELLL,, there is a little trick. You need to read the signals without actually answering the line. The best way to do this is to fool the phone company into thinking you have not answered the line. One very easy way to do this is to get a capacitor and put it in series with the line. I found a .68 microfarad 400 volt non polarized (ie no + on one of the terminals) capacitor (eg from radio shack).--just a cheap mylar capacitor (could even be 200 volts). (but .22 - 4 microfarad also seemed to work). and put it in series with the line. ONe easy way to do this is to modify your wall plug (which has screws ). Unscrew one red wire, and put a capacitor in series with it and the other red wire formerly going to the same terminal. You may want to leave an extension phone plugged in on another outlet so you can hear the ring (and answer any calls you get while playing). Now bring up your zfax and select the voice utilties. pick record voice and select the telco line. then before starting the recording by pushing enter on the OK message, have someone dial your phone. press enter about the time they have finished dialing your phone. This will creat a nice short voice file. PUSH ESCAPE as the second ring starts. This should create a nice 30k file or so with all the info on it. Then play back the voice and start analysing. You should be able to hear it as well as a regular call on your internal modem speaker. The ring will sound like a blast of sound--but not too loud and you should hear a beat of nothing (.5 sec) then beeep(600hz,1/4 sec) beep (1200hz 1/8 sec) bep (1800-2400hz 1/16 sec). I am interested in any voice software people do also. Please send me a note if you have some success. I would also love to supply you with a ZyXEL modem, esp if you are in Canada. (I can provide extra callerid software also) George Vande Bunte PENG OCOMP 416 5341508 gvb@telly.on.ca 238 Davenport Rd. Toronto m5r1j6 Please keep whole file together.