"Hugo Cornwall "The Hacker's handbook"" - читать интересную книгу автора

instructions to change speed under program control. However, to make
full use of this facility, you may need to write (or modify) your
terminal emulator.

Auto-dial - a pulse dialler and associated firmware are included in
some more expensive models. You should ascertain whether the
auto-dialer operates on the telephone system you intend to hook the
modem up to--some of the US 'smart' modems present difficulties
outside the States. You will of course need software in your micro to
address the firmware in the modem --and the software has to be part
of your terminal emulator, otherwise you gain nothing in convenience.
However, with appropriate software, you can get your computer to try
a whole bank of numbers one after the other.

D25 connector - this is the official 'approved' RS232CN24 physical
connection--useful from the point-of-view of easy hook-up. A number
of lower-cost models substitute alternative DIN connectors. You must
be prepared to solder up your own cables to be sure of connecting up
properly.
Documentation I always prefer items to be accompanied by proper
instructions. Since hackers tend to want to use equipment in
unorthodox ways, they should look for good documentation too.
Finally, a word on build-your-own modems. A number of popular
electronics magazines and mail-order houses have offered modem
designs. Such modems are not likely to be approved for direct
connection to the public telephone network. However, most of them
work. If you are uncertain of your kit-constructing skills, though.
remember badly-built modems can be dangerous both to your computer
and to the telephone network.

Test Equipment

Various items of useful test equipment occasionally appear on the
second-hand market--via mail-order, in computer junk shops, in the
flea-market section of exhibitions and via computer clubs.
It's worth searching out a cable 'break-out' box. This lets you
restrap a RS232C cable without using a soldering iron--the various
lines are brought out on to an accessible matrix and you use small
connectors to make (or break) the links you require. It's useful if
you have an 'unknown' modem, or an unusually configured computer.
Related, but much more expensive, is a RS232C/V24 analyser --this
gives LED status lights for each of the important lines, so you can
see what is happening.
Lastly, if you are a very rich and enthusiastic hacker, you can
buy a protocol analyser. This is usually a portable device with a
VDU, full keyboard, and some very clever firmware which examines the
telephone line or RS232C port and carries out tests to see which of
several popular datacomms protocols is in use. Hewlett Packard do a
nice range. Protocol analysers will handle synchronous transmissions
as well as synchronous. Cost: Ј1500 and up...and up.