Picture the evolution of modems

While discussing the speed of things in one of our project I wanted to take a quick glance on the development of communication speed over modems (for copper-based, twisted pair telephony lines.

The picture

Below I pasted a picture that I quickly sketched up to give a glance on speed over copper telephony lines the last few years. There are loads of this pictures of various kinds, but I felt a gap for a more simpler graph… As usual, explanation of abbreviations, etc., etc., are easily found by doing some more googling…

I have picked a few points along the time axes from 1942 to 2004-ish. The bit-rate is plotted, and I have translated them from baud rates were applicable pending on the most common modulation format used. Notice that some of the time points are a bit hard to pin-point, since there is quite a few years between the standard/technique was (experimentally) established and when there were commercially available modems on the market. For example, ADSL was suggested in 1988, but it took until beyond the year 2000 before it is was commercially available at reasonalbe pricing. Same with ISDN and VDSL.

morsecode

The same kind of argument holds for the speed. Some of the standards are not full-duplex, nor symmetric. For example, ADSL offers lower speed for uploading than downloading. In the beginning of the 1960’s the first full-duplex (acoustic) modems were offered at a staggering 300 bps. Further on, some of the standards required multiple lines (in Sweden, for example, telephony was installed with two twisted pairs, backup I presume…) to reach the offered speed.

Indicated in the graph is a clear end. The trend nowadays is not to develop more standards for the copper (rather use fibre or wireless for consumer-market access.

Now to the twist (as always). Some of the Morse code operators were fast, really fast. Actually, in parity with the first modems. The ever lasting record is a stunning 75.2 words-per-minute. Counting low, this would imply something like 75.2×15/60 ~ 20 “dots”-per-second (dots are not necessarily counted as number of hits on the key). But still, the Morse code operator would have to be quite shaky to keep up to speed. The record was set in 1939 and the modem speed in 1942 was something like 25 bps.

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4 thoughts on “Picture the evolution of modems

  1. Pingback: What happened at Bell Labs in 1951? | Mixed-Signal Comments

  2. Pingback: The evolution of making a simple phone call | Mixed-Signal Comments

  3. Pingback: Revisiting the transmission speed | Mixed-Signal Comments

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