When was the automatic loop compensation introduced?

[dsk]

It seems like the US telephones was the first regarding this.   The Scandinavian circuits was best in Europe on long lines for years, somewhere the Brit's took the lead on compensation, and all of us in the rest of Europe stagnated.

Something equal happened with the high impedance ringers. The only thing I have to promote from her is the transistorized dynamic microphone replacing the carbon transmitters from 1967 in Norway.

But we have the common drop of quality when the privatizing started.

dsk

[Jack Ryan]

Auto line length compensation was released in the WE 500 in 1949. It used a lamp filament in its design.

The GPO introduced auto compensation with the 706 about a decade later. It also used lamp filaments - this was about 5 years after lamps (+ve coefficient thermistors) were made obsolete by varistors in the WE 500. Most other jurisdictions didn't implement auto line length compensation until the early 1960s with the introduction of the Assistant and others and their derivatives. They generally used varistors.

Jack

[dsk]

Thank you! 1949 is the first year. And in your answer I got most of the expressions in English I struggled to express in my text. 

I really understand why we didn't put money in this so close after the WWII. But why not later? 

Roughfly: we did "never" implement auto line length compensation, we did not make high impedance ringers (even the 1967 electronic ringer has a REN load approx 2 at full volume) We did omit the problem with bad transmitter quality by making dynamic transmitters with transistors (1967). We did not come up with a std DTMF phone before 1982. ...

dsk

[Jack Ryan]

Thank you! 1949 is the first year. And in your answer I got most of the expressions in English I struggled to express in my text. 

Happy to be able to help!

we did "never" implement auto line length compensation

A lot of jurisdictions didn't use auto line length compensation. In Australia, before the 800, the PMG (the government telephone monopoly) decided that it wasn't worth the money. The problem was only evident close to the exchange and that was a smallish proportion of telephones. It was more cost effective to strap resistors when necessary - that is, when a subscriber complained.

we did not make high impedance ringers (even the 1967 electronic ringer has a REN load approx 2 at full volume)

Perhaps there was no pressing need for high impedance ringers. Did subscribers have more than one telephone? Were there many party lines? Were subscribers able to use phones bought at "Cheap as chips" so that there was a mix of high and low impedance ringers?

We did not come up with a std DTMF phone before 1982

DTMF was introduced much earlier than that in the US and elsewhere but they used LC oscillators using first one transistor and then 2 transistors. They were rather labour intensive. Some jurisdictions skipped the early designs and waited for the integrated circuit designs. What type of oscillators were used in the 1982 DTMF telephone you introduced?

Jack

[dsk]

we did not make high impedance ringers (even the 1967 electronic ringer has a REN load approx 2 at full volume)

Perhaps there was no pressing need for high impedance ringers. Did subscribers have more than one telephone? Were there many party lines? Were subscribers able to use phones bought at "Cheap as chips" so that there was a mix of high and low impedance ringers?

The monopoly supplied all telephones until early 80-ies. 

We did not come up with a std DTMF phone before 1982

DTMF was introduced much earlier than that in the US and elsewhere but they used LC oscillators using first one transistor and then 2 transistors. They were rather labour intensive. Some jurisdictions skipped the early designs and waited for the integrated circuit designs. What type of oscillators were used in the 1982 DTMF telephone you introduced?

Jack

It was some testing from approx 1975, more or less handmade with lots of transistors, later IC's. 
Some circuitry from the first series of the "Tastafon" are shown here:  http://www.classicrotaryphones.com/forum/index.php?topic=14910.msg154687#new

dsk

[dsk]

Forgot: We have never had a REN definition here, but the rule was maximum 2 phones on a line, + en external ringer.  That will bring the REN load  pretty close to 5-ish.

dsk

[dsk]

By some reason the pictures in the link above are not working, try this: http://www.classicrotaryphones.com/forum/index.php?topic=23306

dsk

[Jack Ryan]

By some reason the pictures in the link above are not working, try this: https://tinyurl.com/wh4oqrc

dsk

Perhaps the original thread was moved Dsk, I don't know.

As an aside, shortened URLs are convenient but they are also opaque. As I can't see where they lead, I don't click them.

Hope you are enjoying a Christmas break. We had a cool change for Christmas day (35C) which was welcomed. The week before was in the 40s with a peak of 46 where I am and the low 50s in regional areas. This week we are back in the 40s.

Regards
Jack

[FABphones]

By some reason the pictures in the link above are not working, try this: https://tinyurl.com/wh4oqrc

dsk

As an aside, shortened URLs are convenient but they are also opaque. As I can't see where they lead, I don't click them.

Agreed re tiny url, thankfully this one leads here:
http://www.classicrotaryphones.com/forum/index.php?topic=23306