 Our speaker Christian Berger is an engineer of technology and he will talk about fax signalising. Hello and welcome to my presentation to the subject of long-distance copiers of group two, three. It's a subject that was quite controversial throughout the time of the Congress. In the USA there is an anti-faxer organisation who wants to work against long-distance copiers. And I want to show you some examples of fax configuration. Don't be afraid, we are not going to use the long-distance copier. A part of the usage data, fax devices also need to have some technological parameter they have to exchange, so the meter data. The easiest access to this information is on the devices itself. Many devices can print these sent information. Each sequence here is within this fax device itself. In the beginning the receiving fax device sent its ID and some information and then the sending fax sends a lot of data. We send a lot of binary zeros to verify the connection. Then we send information, then we send data and all the information the page is over. The receiving fax acknowledges the reception of the page and the sending says goodbye. The signalising data are modulated according to one type format. We change the zeros and ones to different tones. Then we have a modulation on top of that. We have the stream of top and the bits below. HDL allows us to send data on a synchronous channel. On a synchronous channel we always transmit all the bits at one unit of time, always the same number of bits, whether we have any content or not. In the time when no data needs to be transmitted we send a flag sequence. This sequence is zero, six ones and once more zero. We always repeat it and transmit it repeatedly if there are no usage data. If we have data we need to transmit and they have different zero and one bits. To differentiate them from the flag bits, every five ones we add another bit. It's always zero and allows us to check whether it's a number of ones behind each other or a flag sequence. The beginning there's always a header and a 16-bit checksum. The header contains an address field, eight bits, usually all bits one, a few use facts and a control field. The control field contains about what type of message is transmitted and whether that message is the last message in the sequence. Within the frame all data are sent with their additional bits to ensure not enough too many ones are there. There are no start and stop bits because we have the flags to differentiate between the frames. This example shows the most simple case. We just sent all the data, the receipt is confirmed and the connection is closed. If there are bit errors in this case they lead to image errors. They are sometimes detected in the receiving fax because we do not, if the length of a line is wrong, but we can't request further lines. The received fax can only, if there are too many wrong lines, the connection can be closed. To be able to send fax over bad lines we are able to use ECM. The image data is put into HDLC frames and they have a checksum and at the end the receiving fax can request the sending fax to recent invalid blocks and that is repeated. So long until all pages are received correctly. There are also further information like fax, color fax or voice data. That means it's hard to hide errors in these other methods so it's important that the connection is correct and ECM makes sure that there are no unknown errors. That also means both fax devices need to have the memory in memory and in the 80s that would have been much the expensive. Nowadays in Voice of IP there are additional problems for the fax. So voice of IP protocols like ZIP transport the data using RTP. That means the data is taken into 20 millisecond long chunks and they are put in a UDP package with a header and this package is then transmitted. The receiver receives all these packages and packs them, writes them into a buffer and then returned into audio data, to an audio signal. However what are 20 milliseconds? Quars or oscillators have the issue that they have a different speed. So 20 milliseconds for one receiver might be slightly different than 20 milliseconds at the center side. That means that it's the issue that the data is received and sent at different speeds. That means that it's possible that the waiting buffer is too full or too empty. So additional data needs to be added or removed. That has an illegible effect and you can even optimize it in such a way that the gaps only happen when there is no speaking. However modems and especially with the long distance copier we have a long time where a modem is talking and modems have an issue when there are short losses of information. They need to be synchronized with all the data and if data is lost the modem is not synchronized with the sending modem. That leads to a lot of bit errors which lead in some cases to a loss of the connection. To reduce the issue T83 was developed. The idea behind T83 is that we circumvent the modem. We try to connect the computer of one fax device to the computer of the other fax device. That leads to the circumvention of the modem issues. Another situation is that less data needs to be transmitted. We do not need a full data connection but only need to transmit the used data. In addition we can even add redundant data just in case a package is lost. Wireshark is able to decode T80 data. And here you can see how the signal data is transmitted. Because signal data is with 300 bits per second every single octet is transmitted. That also reduces the latency that might be included because fax is real time fax. Other messages indicate whether a modem should be turned on and off. Otherwise it's like any other fax data. We also see the zeros that are connected to verify the connection. We did that implemented because we have T83 gate base that should be implemented to ensure that only one side talks T83 and the other one T30 the old standard. The initial idea was that fax devices in the future are able to speak voice of IP addresses and are able to be connected to the internet. The communication with older fax devices would be used through a digital modem in the devices or through T83 gateways. Unfortunately there are very few internet aware fax devices. So apart from some fax servers there are very few devices that speak IP directly. There are also further fax devices. For example the German weather service sends weather fax through short wave. Also the fax device in the space lab is probably not a group 3 fax. That is my short introduction in the signal information in group 3 long distance copier. I hope you enjoyed it. Use the power of the tether fax. You will see what is possible with these communicative secret weapon. Thank you very much for your attention also from the translation booth from me Franz T. If you have feedback use the hashtag C3Lingo. I hope everybody else learned as much as we did today. Okay back to the questions. Because we don't want to go too far over the 40t to minute. Why are they T83 over VoIP? Why was that specified? Because T83 over SMTP was already specified. Do we want to have real time fax? It means the moment when it scanned the sender prints it already or do we want to have something similar to email where we basically send an image via email. It is the disadvantage that we can't be sure that the fax was received. I do not know whether there is a sender recognition exchange in appropriate manner. However it is not used. A large issue is all the practical implementation because we have a physical fax device that is in some company already and T37 we would need very extensive methods. We would need to save the document before sending it. This is the smaller variant T83. Part of that is what do I do if I have a fax with 300 dpi but the other side just says 200 dpi and we had to calculate the difference. There are fax to mail implementations but they are completely different issues. There are advantages and disadvantages. The next question. What about group 4? What is group 3? Where are the other groups? I have never heard anything about group 1 or 2 fax machines. Group 4 is through ESDN but they are very rare. A group 4 fax wants to be connected to ESDN directly and then we have a transparent 64 bit data channel and would be a lot quicker and would suddenly have a lot of special features like text transmission or arbitrary file transmission. There are digital group 3 faxes, a couple analog fax devices that they still scan the image line by line and then the printer prints it in real time however. We are not talking about pixel or there is no data compression and that is used by the Deutsche Wetterdienst, the German weather service for weather fax. Another question. What is weather fax? Oh yeah, weather fax. The idea is very simple. We have for example ships on the sea and they want to know how the weather is going to be because if they are streaming ahead it is very important. You can call them up but the weather map is much more handy. So the Deutsche Wetterdienst has a short wave sender and it sends the weather maps all over the world and you can get a nice image of how the weather is going to be. Cool. The next question. How can I have a GPG-appropriate fax encryption? How does fax 3 encryption work and how does the key exchange work? That's an interesting question. It's defined in T4. There is a definition I have not looked into it yet because I do not believe that there is a fax device that supports this but hypothetically we have fax encryption. What group of devices? The Fritzbox. Fritzbox itself has many functions. It's also a router but it supports fax group of group 3. I do not know whether it might support fax group 4 but hypothetically we could also send group 4 fax via transparent data through voice of IP however usually it operates like a group 3 fax or as a 38A if you activate 38. When can we use T38? It needs to happen. Is it dependent of the provider or fax device or router? That depends on a lot of specific locations. Ideally T38 is from one end to the other end and we have a voice of IP connection between those two and in addition we need to be codec transparent. That means if one device requests T38 that needs to be transparently connected to the second device and that needs to be answered that it is transmitted appropriately. There are service providers that do not offer this and there is an asterisk in between and that does not transmit the request. You can then turn T38 back to normal voice data but there is always some loss and that leads to faxes arriving with a reduced probability. So hypothetically it should work if you have two Fritz boxes at a German telecom and the T38 connection should reach through. Among provider it is even more questionable. Perhaps there are other connections where T38 definitely does not work. And then there are two more questions. First of all where can I find the T4? T4 is available on a home page on a website but I don't know the website. If you look IUT-E and then T.4 you should find the specification or search for T.30 and you will find the fax standard and there is a list with all the T standards and you just click on them and get the PDF. And then are there details to T38 on the Fritz box? You know some details about it. It's a question what details are interesting about it. I happen to know that the Fritz box actually don't support one specific modem standard. It's a bug in the Fritz box and it's already reported and so far it just wasn't fixed. And it's V17 with 4,000 bits per second. It's a rare standard but the Fritz box does not support this standard therefore transmission to this data standards are not possible. But I don't know further details. It works quite well with the Fritz box. The Fritz box is a German router manufacturer AVM is the name of the modem. Thank you very much. Perhaps you led to one or the other person being more interested into faxing. Thank you for having me here.