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Acoustic Coupler Help

Chuck(G) said:
...companies had access to Centrex telephone and their own private set of tie lines. (After hours, this was handy if your relatives lived in a city served by the company Centrex--you'd simply dial a string of numbers and then get an outside line at the far end. Bingo--free phone calls). I used to have fun while waiting for things to happen by figuring out the most circuitous path through the system, making the phone on the next desk ring. Someone would pick it up and it would sound like I was calling from the other side of Mars, barely audible over the line noise.
Click to expand...

That raises the topic of "phreaking" - the first famous amateur network hacking of phone networks, usually by manipulating the DTMF dial signals. Audio-encoded digital signals is the inverse of todays packet-switched digital-encoded audio, but it brings us right back to the topic of audio-couplers.

Rick
 
Thanks - interesting. The "signal" channel overlaid on the voice channel grew a whole lot of functions beyond just the transfer of billing-related information. As network switching automation became more complex, the signal channel would also carry routing information and, in support of that, some levels of QoS information. In the POTS, that overlay multiplexing technology evolved into ADSL.

The current generation of smart-phone users, addicted to text messaging, are mostly unaware that the text capability was originally included in the global mobile network standards solely for the carriage of (mostly automated) administrative messages between network operators. It took some years before someone (at Nokia or Ericsson, I think) suggested allowing customers to use the "signal" channel on digital phone networks to send short text messages to other customers, and even more years before networks agreed to exchange text message traffic. Now text messaging is the single largest profit centre of the mobile phone businesses, and also the parent of Twitter.

Rick
 
The "genius" in texting was charging for each message. An old Register article has the cost of sending an SMS message more than sending data to the Hubble Space Telescope.... ;)

After the raging success of SMS messaging, it's no wonder that carriers are now wondering how they might work the same miracle with internet connectivity....
 
Hi I ran across your blog and wanted to fill you in on the TC3001 Originate Acoustic Coupler that we invented and build in my first modem company. It was mainly sold with DEC Writer LA36 printers that were widely used in the credit industry. that is why the 20ma current loop interface was on the rear panel. it was a mating connector for that printer.

We sold 1000's of them from 1976-1980. this was before you could directly connect a modem to the telephone lines and could only connect via a telephone handset using the handset microphone and speaker. Many persons used them to log into the early time shared computer services before the PC and mini computer market emerged.

If you want assistance with operating it, the other founder of the company is still working in the modem field and I can put you in touch. Please advise.

Bob Way
 
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