More on the SxS switching: On the old exchanges it wasn't at all unusual to hear a little crosstalk from other lines, and the step-pulsing sounds of other calls being set up could often be heard in the background. Here's a recording of Step-pulse crosstalk on an otherwise quiet line.
When you were calling "digital - digital" the number usually just rang out immediately but when calling digital to ARF / ARK crossbar or to a mobile or abroad (e.g. to the UK to an old switch) the bebebebe tone was played down the line rather than letting you hear the actual signaling.
The pre-digital exchanges here didn't let the caller hear the signaling, but there was no "call progressing" tone applied. However, the AC9 signaling system -- which was very widely used for many years in the U.K. -- used 2280Hz for supervision, and you would often hear the chirp of 2280 on a trunk call when the distant party answered.
One thing that was done on British crossbar exchanges was the application of a long first burst of ring-tone when a call switched through before dropping into the normal ring cycle.
The idea was to prevent extra delay if the call happened to switch through during the silent period between rings, although considering that the break between rings on the British/Irish cadence is only 2 seconds, it probably wasn't that big a deal. SxS switches never adopted this approach.
In other countries if a switch is swamped it just won't give a dial tone at all. Here the switch will take the call, let you dial and then make you wait until it's ready to process the call.
Digital switching has resulted in a vastly different network compared to the older switching systems.
In SxS without directors, the dial pulses control the selectors directly, so the only way to ensure an instant dial-tone to all subsscribers without fail would have been to provide one first selector per line.
In director areas (which in Britain were just the big cities: London, Birmingham, Edinburgh, etc.) it was the director which provided dial tone and accepted the dialed digits, storing them until enough were received to pulse out the correct routing codes into the selectors. Directors were complex and expensive pieces of equipment, so optimizing their use was essential, and providing one per line was totally out of the question.
In TXK (crossbar) exchanges, a similar situation existed with the register-translator. As with the director, this stayed on the line just long enough to accept the dialed digits and set up the call path before dropping out to be used by another caller.
On some small SxS offices you could sit listening to dial-tone all day, but on director SxS or crossbar if you hadn't dialed after at most 30 to 60 seconds, you'd be dumped off the director or register-translator to free it for other calls.
Where circuits were all busy at the moment a call was dialed, there was no question of waiting for a line to become free. The equipment just connected Equipment Engaged Tone to tell the caller to try again.
If the congestion was on routes out of one of the big tandem centers, then the caller would be given the luxury of a recorded message, such as this .
The electromechanical switches here were pretty different. SxS disappeared very early on when the network began to be digatlised in about 1979-80. The priority was to remove the SxS switches as they were becoming old and extremely unreliable. P&T (the predecessor to Telecom Eireann, now Eircom) operated a horrendously bad network at the time. Parts were also becoming difficult to come by and it was generally a maintenence nightmare.
However, P&T had installed a signifigant number of large crossbars, ARF (local) and ARM (transit) particularly during the 1970s.
These switches were pretty efficient, reliable and effective so remained in service along side digital switches albeit only as local exchanges right through the 1980s gradually disappearing by the early 90s.
Ericsson also offered a seamless upgrade path from ARM/ARF to AXE where by digital equipment could gradually replace various parts of the older switch until eventually it could be cut over to being a full AXE.
The smaller Ericsson ARK crossbars used in some rural areas generally were replaced by Alcatel E10 systems as almost all of rural ireland operates on that system. SxS switched areas generally became E10 too.
ARF went through a period of being ARE-11 which was a kinda hybrid of a crossbar but with computerised registers etc. So you picked up, dialled this was handled digitally and a computer system controlled the switch.
These switches sounded exactly the same as the older ones the only difference being they handled DTMF & were marginally faster.
Occasionally ARF switches could go wrong and give youa blast of really rapid MF signaling strings all sounded very high tech, but wasn't compared to SS7 The exchange used these internally to control various moduels and also to signal the network. Not sure which signaling system it actually was.
Also, compared with most of the rest of Europe digialisation occured much more quickly and much earlier on. Most of the system was fully digital by about 1987 with the remainder being ARF but only locally. All ARF exchanges were working effectively as remote concentrators for nearest AXE or E10.
Also that long burst ring tone is very familar. It's used here as standard the long burst activates caller ID equipment on the line.
Here in Austria digitalization officially started in the mid 1980ies, but the last remote parts of Vienna were analog until 2001 or so, and I even suspect there are still some analog exchanges in rural areas (at least the numbering scheme indicates it). In Vienna analog lines were pretty easy to spot because they usually had a slightly different numbering scheme. Single lines had a 6 digit number, party lines were 7 digit. Digital numbers are all 7 digit, but some combinations aren't used any more, for example the 42x, 43x, 45x and 46x range disappeared completely. 42 and 43 were usually moved to 40x (single lines were usually just extended to 402x and 403x, new numbers are in the 405x to 408x area). In rural areas all (or most) 3 digit numbers are now 4 digit (spoiled some quite cool numbers, for example 555 is now 7555), but in some remote places there are still 3 digit numbers, even though I definitely know they were supposed to be changed to 4 digits years ago. So maybe these areas are still analog. Or they just didn't see any need to change the numbers because of all the new cell phones, so maybe they didn't need the extra capacity.
We never had less than 5 digits in rural areas but, for some reason, they're merging most of those areas into single area codes and making them 7 digits.
Very geographically structured system still though.
01 - Greater Dublin Area 02 - Greater Cork Area 03 - "doesn't exsist (yet)" 04 - North East (& NI 048) 05 - midlands & south east 06 - South & Mid west 07 - Northwest 08 - Mobile 09 - West Each of those codes, except dublin is then further divided into 10 areas e.g. 021 to 029.
Special services / freefone etc all start with 1 1-800 (Freephone) 18 50 & 18 90 (local rate) (eighteen fifty and eighteen ninty) 15 XX XX XX XX (premium rate 30¢ to 200¢ per min) e.g. 15 50 30 30 30 (fifteen fifty(tm) 30 30 30)
with mostly 7 but some 5 digit numbering.
The plan is to move it all to
0XX - XXX - XXXX
they've also removed 4 digit area codes like 0506 this year.
[This message has been edited by djk (edited 09-16-2003).]
[This message has been edited by djk (edited 09-16-2003).]
A mixed number system was always a feature of the British network. Many rural areas served by a UAX (Unit Automatic eXchange) had 3-digit local numbering into the 1980s.
One consequence of the heavily Strowger-based network with no directors in most areas was that we had many local routing codes.
In addition to the list of national STD codes, everybody was given a book of local dialing codes, which varied from exchange to exchange. Typically, a small outlying village exchange would dial 9 to reach its parent exchange, and from the group center you would dial a two-digit code, often 8x but sometimes 5x, 6x, or 7x to reach neighboring satellite exchanges.
Fictitious & simplified example:
Subscribers in Big Town would be told to dial the following:
Little Village, dial 81 plus number Tiny Hamlet, dial 82 plus number
Subsscribers in Little Village would get the following instructions:
To call BigTown, dial 9 plus number To call Tiny Hamlet, dial 982 plus number
At each GSC, there were other codes (generally 9x) to reach adjacent GSCs which were in a different STD code but still within the local call area.
Sometimes there was sufficient traffic between small, neighboring exchanges to justify a direct trunks between them. So if Little Village and Tiny Hamlet often had calls between them, there might be a few direct trunks and callers in Tiny Hamlet might then be told to dial 6 plus the number to reach Little Village.
If those direct trunks were all busy at any time, those in the know could dial 981 instead (unpublished code) and route the call via Big Town.
Some routes would be barred from incoming trunks, but the dial-through nature needed at many locations meant that this was not always possible.
As a result, one could set up local calls via a very convoluted path. From my home in the early 1980s, for example, the direct way to dial Zelah 299 (a test number in the small Zelah exchange) was to dial 54-299.
But I could also get there by dialing something like this:
We used to have a bunch of those short area codes in the Vienna area too. I think to vienna was 9, Vienna to baden was 96 and Vienna to Wiener Neustadt was 98, but I'm not exactly sure. These codes disappeared about 10 to 15 years ago. They had 1 to 3 digits and all started with 9.
We never had that.. however, i do remember when you called from a very old switch in a town we had a holiday home this is what would happen.
you dialled say 39999 (pulse) the dial tone would go away.. then you'd hear another dialtone and the whole number being pulsed out.. then bebebebe and ring..
it was actually just dialing out on an E10 exchange! Pretty much behaving like a glorified 1950s analogue PABX.
Anyway, if you dialled 39999 and then very quickly tone dialed before it started sending the pulses you could continue tone dialling (the E10 would ignore the pulses) so you'd end up getting any call you wanted for 11 pence All the stingey backpackers knew this!
All that stuff is LONG LONG gone now though. I think it was prob. one of the only very old switches left in the country, no idea what it was even! could have been old xbar or even SxS.
Telecom noticed the payphone billing discrepencies and suddenly all the payphones went over to digital lines, presume they just passed through the old switch.. and with in a few weeks it was fully digital.
Obviously i have never done this myself, but i was told about it by a tourist!!!
The 2600Hz supervision with MF in-band signaling on many American trunks resulted in the infamous "blue box" which enabled free calls to be made.
The device wouldn't work in Britain due to the different signaling systems, but the "black box" would certainly work on the old GPO system here.
As none of this is applicable to the modern system, it won't hurt to reveal the details.
The black box enabled free calls to be made, the only catch being that the device had to be located at the receiving end of the call. The trick involved was to use a fairly high value of resistance across the line, low enough to trip the ringing on the final selectors (i.e. cut off the ringing voltage to the line), but not low enough to complete the DC loop to signal an off-hook condition. It was the the latter which sent a supervision signal back to the originating exchange to indicate "call answered" and to start charging.
Having tripped the ringing, it was then possible to connect an audio path via isolating capacitors to the line and talk both ways. In some cases, the connection would time-out and release after a minute or two, but of course somebody could just call back again -- Hey, the calls were free!