1. a MODEM Story
or The Perils of International Support

2. POTS
VAN
Using telephone set, dial a local number which you reach through the local telephone system, a.k.a. “POTS” or “Plain Old Telephone System”
An interface device between POTS and “Value Added Network” answers the call with a whistle.
Press a button on the desktop phone set and the connection is switched to the modem which in turn is connected to the terminal.
Proceed with LOGIN etc.

3. It still required establishing the connection manually.
POTS
VAN
In the mid-70’s the requirement that only AT&T devices could be connected to their network was removed. This Texas Instruments “Silent 700” portable terminal was introduced in 1978 and was very popular. It was light-weight, used thermal paper (similar to fax) and had an integral modem connected to the telephone handset via an acoustic coupler. It supported 120 cps compared to the 15cps of the teletype.
It still required establishing the connection manually.

4. In 1981 Dennis Hayes, a computer hobbiest, introduced the Hayes Smartmodem 300.
In addition to the modem’s communications functionality, it included a control interface that eliminated buttons and switches, instead it allowed the connected terminal to send text ‘commands’ to set configuration values and/or establish a connection. To do this he defined the “AT” (attention) command language which became the de facto standard. Over the years speeds increased to nominal 56Kbps, perhaps a realistic 4,400 cps, but broadband ‘always on’ cable modem and ADSL technologies eventually made dial-up obsolete.

5. Very Basic Example Command: ATe0v
Attention: turn off Echo, and give verbose responses
Expected Response: Ok
Command: ATdt9,
Attention: dial, touch-tone, 9 then pause, then
At this point, unless you turned off the speaker, you should hear this:
Expected Response: CONNECT speed
or BUSY
or NO ANSWER

6. Around 1982 I developed a software module that linked our host-based graphics programs to an on-site HP 8-pen flat-bed plotter. Most customers had their charts printed at the data center and then FedEx’d them as while it didn’t cost much to create the chart, the connect time to print it via a dial-up network connection was cost prohibitive.
In 1984 the company sponsored a contest and I proposed using a PC to emulate HP plotter devices and by doing so capture the instructions to a local disk. This is similar to ‘spooling’ for a printer, and thus permits delivering the output while off line, with the additional option of delivefing multiple copies. To do this I had to make the PC seem to be an HPGL device from the viewpoint of the mainframe computer.
I hadn’t gotten very far into the project when I realized that as long as I was at it, I might as well implement a module for the HAYES AT command set as well to allow for full automation.

7. I won the contest, and got an additional bonus for the communications module as it became a component of our pre-internet private product offering. It was installed on thousands of machines distributed in more than 60 countries. All was well until we got a message from a customer in Paris…

8. MODEM NOT RESPONDING
This was curious as:
Of the 14 machines at this site, this was the only one that didn’t work properly.
This machine communicated through the modem properly when running an ‘in house’ application, that the 13 others did not use.
The on-site representative from France PTT assured me that their 14 modems were the same and that they were all HAYES AT command set compliant.

9. I sent our technical support representative a replacement modem script that displayed all data exchanged between the PC and the modem. Here’s what he got…
ATe0v
Oui
MODEM NOT RESPONDING