04-03-2011
FYI only, on ATMs, POS machines and modems:
Ref:
US Robotics on Modems and POS
Quote:
Modems allow the PoS computer to communicate with the banks or credit card processing centers to get the transaction approval. The modem also allows daily transaction totals to be sent to other locations within the company such as corporate headquarters. Modems can be embedded within the PoS computer system or can be attached externally to the PC.
Many systems use LANs or Local Area Networks to transfer the data locally via an Ethernet cable instead of using dialup modems. This type of connection is ideal for systems that have multiple computers that need to access the same information such as restaurants, but ultimately the call for card approvals is still sent via a dialup modem
.
Quote:
So why still use dialup?
There are 3 reasons to still use dialup modems: minimal data and speed requirements, cost associated with setup, and security of a on demand connection.
Most current modems transfer data up to 56 Kbps, but the PoS systems don’t always require those kinds of speeds. Transactions are normally quite small and may only require 300 bps up to 2.4 Kbps – only a fraction of what normal dialup modems can support, so 33.6 Kbps modems can be used with no loss of time. The 56K modem connection allows some of the more sophisticated PoS systems to transfer more data and utilize the faster connection speeds.
With these small amounts of data and minimal speeds needed, the faster Ethernet networks are not needed and the dialup solution can be much cheaper to implement. Most businesses need to be able to accept card transactions, and installation of a simple dialup PoS terminal may only require a dedicated telephone line, whereas installing a network and paying for business quality broadband service could be quite expensive to set up as well as the higher fees each month. In addition the nightly transaction summaries sent out can be scheduled during off peak hours which can also save even more money.
Connecting only when you need to also insures better security. The “always on” broadband connection means the computer and PoS system is constantly connected to the Internet with makes hacking and security breaches a higher threat. With dialup the computer is only connecting to the Internet just long enough to complete the transaction, making hacking into the terminal very difficult.
The same POS arguements above are also true for many of the ATM machines we see all over Asia in gas stations, small grocery stores, etc. Almost all of these use dedicated phone lines and modems.
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LEARN ABOUT POSIX
dialups
dialups(4) File Formats dialups(4)
NAME
dialups - list of terminal devices requiring a dial-up password
SYNOPSIS
/etc/dialups
DESCRIPTION
dialups is an ASCII file which contains a list of terminal devices that require a dial-up password. A dial-up password is an additional
password required of users who access the computer through a modem or dial-up port. The correct password must be entered before the user
is granted access to the computer. The set of ports that require a dial-up password are listed in the dialups file.
Each entry in the dialups file is a single line of the form:
terminal-device
where
terminal-device The full path name of the terminal device that will require a dial-up password for users accessing the computer
through a modem or dial-up port.
The dialups file should be owned by the root user and the root group. The file should have read and write permissions for the owner (root)
only.
EXAMPLES
Example 1: A sample dialups file.
Here is a sample dialups file:
/dev/term/a
/dev/term/b
/dev/term/c
FILES
/etc/d_passwd dial-up password file
/etc/dialups list of dial-up ports requiring dial-up passwords
SEE ALSO
d_passwd(4)
SunOS 5.10 4 May 1994 dialups(4)