The modem uses data compression technology that in some cases will double its speed.
The two modems used different - and incompatible - technology to transmit data.
The modem only uses frequencies above 8 kHz, to avoid interfering with normal phone service.
The regular phones also have two lines in Hilton rooms, so a modem can use one while the guest talks on the other.
Fax machines and modems, due to their inability to ask for a party by name, use the station-to-station technique.
The modem will use a control slice to signal a RTS(request to send) to the headend.
Newer modems use nonvolatile memory to hold this behavior, which can be manipulated with the AT&W command.
I anticipate that he took precautions first, probably bouncing the signal around from country to country, from whatever phone number his modem is using.
Today almost all modems still use a variant of the Hayes command set introduced in the Smartmodem.
For example, many modem, network, and TV cards use this form factor.