The history of private datacommunication 4278

Peter Bj¿rn Perls¿ For the UK, I have online a manual on Post Office Datel services dated May 1973, which gives an overview of the data services available and viewer ( Linux-Unix, Mac OS X and Windows), if you are interested. The manual can be found at:-

Along with most(?) European contries the telephone system in the UK was Government controlled and run by the General Post Office (before being privatised as British Telecom in the 1980s). Under the GPO, there were many restrictions and only equipment supplied and conected by them was allowed to be used, and that equipment tended to lag behind technology being produced by the private sector. It also was expensive.

At one organisation where I was a systems programmer for the 1900 mainframe (and general 'techie') we were have Tariff 'T' lines (4-wire data grade private circuit) installed between ther computer centre and remote offices, each line to support 1 terminal (VDU) running via 1200 bps modems into a mini-computer (CMC) running a single application.

The first few lines were installed and worked without any problems. The next line was to an office on the same site - I could see the roof of the building from my office window and it would have been possible to throw a cable between the roofs of the buildings, but not allowed.

This line would not work. We had various engineers in, each testing their own bit. The line engineer tested the line and proved it working and blamed the modems, the modem engineer tested the modems and blamed the line, and so on.

After a few weeks I got fed up chasing them and took my own test gear in (a simple signal generator and signal tracer). A couple of kicks to the Line Termination Rack and the back fell off. As the back had fallen off, I decided to have a quick look inside and poke around.

A quick test showed that the incoming line was okay to the rack, but didn't pbutt through it. A bit more poking found the fault, the impedance matching transformer didn't have the 'strap' to match the line impedance fitted.

In fact the only line positions to have this strap fitted were for the first 4 lines installed, the other 16 had been left off. I later found out that these should have been fitted to the modules in the workshop, before the rack was buttembled. The strap was less than an inch long and a pig of a job to fit in an buttembled rack, but fairly easy to unsolder one end and resolder it to the appropriate tap. A case of a lazy workshop engineer.

My next problem, after refitting the back, was how to tell the engineers where the fault was without admitting tampering with GPO equipment. They were quite pleased to be told what the fault was, but unhappy with their colleague in the workshop. This strap was never checked by any of the engineers as it fell between their 'domains'.

I'm sure that this sort of thing doesn't happen nowadays, or does it?