In 1975 I developed the “Tillegraaf” baseband modem at the AKZO chemical company research laboratoria in Arnhem NL , to be able for us to connect asynchronous TTY compatible computer terminals and measuring equipment in our factories and offices (and within cities between offices) using the then state ministry of PTT owned copper phone-wires. It was faster (19.200 bps), less expensive and had a better electric separation (preventing ground loops and lightning damage). My novel approach was to use optocouplers instead of transformers to get electrical de-coupling of the sometimes long and interference (lightning etc.) prone copper wires on factory plants. Price we payed was 2 separate power units. Another success was that I did get it through the PTT approval process which allowed it to be used on PTT owned inhouse and local unloaded (not-pupinized) twisted pairs. It has [ PTT Toelatingsnummer 770502/TG1 ] **). Nowadays PABX phonewires are property of the owner of the private property and you have to lease local lines from KPN, for instance for ADSL.
About 50.000 where manufactured under licence by Enraf-Nonius and sold by Vosko Networking BV, in Germany and the Netherlands. In Germany Deutsche Telecom (FTZ) *) forced us to put a circuit in to prevent it from operating at faster than 4800 bits/second on Deutsche Bundespost (now Deutsche Telekom [DT]) in-house and local phone wires (2 copper twisted pairs). This photo shows the prototype with the extra “Bremms Schaltungs” peed cut-off board on top.
I also invented about 1977 the “Plector(r)” multiplexer, sold by Vosko too, which could connect 8 asynchronous computer terminals (TTY compatible with ASCII 8 bit start-stop characters) over one Tillegraaf(r) line. It implemented 8 UART’s to synchonize the character streams into 1 fast UART that functioned as parallel to serial converter.
These devices did transport more data in those days than all the other local and wide area data networks of companies on PTT lines in The Netherlands added together.
Biggest incentive to develop the Tillegraaf was that it saved approx. 2000 Euro’s per terminal (most of them Digital Equipment DEC VT100’s or HP minicomputer terminals) connected compared to local links using the very expensive line drivers sold by Philips-Sematrans. Since the AKZO company (now AKZO Nobel BV) had a policy of not paying inventors in their laboratories extra for inventions for which they where hired in the first place, I put my name in: TILLegraaf. And I arranged that the royalties came in to the department account of my boss, which gave me extra freedom to explore things I considered important. I still do.
ir. Jaap van Till, theConnectivist
*) It took me about a year of my life to get the so called “FTZ Nummer Genehmigung” for it. The Fernmelde Technisches Central Ambt in Munich had set up a neat Franz Kafka construction for me. They told me that for inhouse copper wires from Bundespost or others we formally needed no Bundespost approval, while knowing quite well that no German would even dream of connecting any device to a “telephone line” without a FTZ number on it. After some mental arm wrestling I however did get the FTZ number, but they took revenge by insisting that in Germany on Bundespost kabels the jumper on the “Brems Schaltung” must be set to prevent links going too fast. I am not sure it was bacause no German manufactured baseband modem could work as fast as the Tillegraaf or that the higher speeds could not be wiretapped and listened in to with their equipment at the then dazzling speeds of 9600 bps or 19.2 Kbps 🙂
**) TG1 refered to PTT Dept of TeleGrafie (distance writing) which performed admission test for modems on the Netherlands Telephony network. Hence the name TilleGraaf . The rumor that I put GRAAF in because of my ambition to be upgraded by the King from baron to graaf van Till is false.
The Tillegraaf contained another trick, added by mr. Korzilius of our Arnhem laboratory: resistors on the twisted pair lines. In case one of the 4 wires broke or was cut the input of the receiver would not produce a flood of random bits into the connected computer, but would be jerked sideways to a zero voltage position. This is why TG1 admitted our apparatus and rejected other designs, by Hoogovens and by PTT itself, which where entered about at the same time. Yes the devil is in the details.