Data modules and asynchronous data units
555-233-116
48 Issue 4 October 2002
Understanding RS-232 communications
To install a data module, you have to set up the device to work with RS-232
devices.
NOTE:
Data modules, PGATE boards, printers connected through data modules,
SATs connected through data modules, and anything related to the X.25
connectivity protocol are not supported on the S8300 o r S8700 Media
Server platforms.
The RS-232 communications protocol defines a commun ications link as a Data
Communications Equipment (DCE) device and a Data Terminal Equipment (DTE)
device connected by an RS-232 cable. The send a nd receive pins on DCE
equipment (pins 2 and 3) are reversed on DTE equi pment, so that the DCE
transmit pin connects to the receive pin of the DTE and vice versa.
Generally, the term DCE is applied to devices that mediate between custo mer
equipment and the carrier or network. Such device s include modems, data
modules, and data units. DTE describes devices that p rovide a user interface for
data communications, such as dumb terminals and PCs. W hen configured as
DTE, data modules are used for asynchronous modem po oling. When configured
as DCE, data modules are analogous to modems in that they link a device such
as a terminal or PC (DTE) to DEFINITY.
To install a data module correctly, you identify the connected equipment as DCE
or DTE and do one of the following:
■Configure the modem for a DTE or DCE connection
■Install a null-modem converter
Detailed instructions are provided for each modem type, beginning on page 49.