External Connections - Quatech QSC-100 User Manual

8 External Connections

RS-232-C devices are classified by their function as either Data Terminal Equipment
(DTE) or Data Communication Equipment (DCE). Generally, data terminal equipment is
defined as the communication source and data communication equipment is defined as the device
that provides a communication channel between two DTE-type devices.
Terminal
DTE
Terminal
DTE
Figure 16 --- Use of DTEs and DCEs in a communications link
DTE- and DCE-type devices have complementary pinouts to allow terminals and
modems to be connected directly using a one-to-one cable as shown in Figure 16. In many
applications, DCEs are unnecessary, and in these cases a cable called a "null modem cable" or
"modem eliminator cable" is used to directly connect two DTE-type devices. A typical null
modem cable is also shown in Figure 16.
(3) (3)
RxD RxD
(2) (2) TxD TxD
(4) (4)
RTS RTS
(5) (5)
CTS CTS
(20) (20)
DTR DTR
(6) (6)
DSR DSR
(8) (8)
DCD DCD
(22) (22) RI
(7) (7)
GND GND
Typical DTE-to-DCE cable
Figure 17 --- Cabling requirements for RS-232-C devices
Quatech QSC-100 User's Manual
Modem
RS-232-C
DCE
Modem
RS-232-C
DCE
(3)
RxD
TxD (3)
(2)
(2) TxD
RxD
(4)
(4) RTS
CTS
(5)
(5) CTS
RTS
(20) DTR
(20)
DSR
(6)
DSR
DTR (6)
(8)
DCD
DCD DCD (8) (8)
(22) RI
RI RI (22) (22)
(7)
GND
GND GND (7) (7)
Typical DTE-to-DTE null modem cable
(cables using 25-pin connectors shown)
Get other manuals https://www.bkmanuals.com
Telephone
line
(3)
RxD
(2)
TxD
(4)
RTS
CTS (5)
DTR (20)
(6)
DSR
(8)
DCD
RI (22)
(7)
GND
24