MODEX-OPTS, MODEX-OPTM
User’s Manual
Section 4. Installation
Page 27 / 113
4.2. Serial devices
4.2.1. General information about serial communication
There are two kind of devices in general serial communication from our aspect:
Data Terminal Equipment (DTE)
DTE is an end-instrument that converts user information into signals or reconverts received
signals. Typical DTE devices: computers, LCD touch panels, control systems.
Data Circuit-terminating Equipment (DCE)
DCE is device that sits between the DTE and a data transmission circuit. It also called data
communication equipment and data carrier equipment. Typical DCE devices: projectors,
industrial monitors and amplifiers.
Among others the pin assignment is different between DTE and DCE and different type of
serial cables have to be used between the serial devices.
DTE
DCE
DTE
DCE
Pin2
RD
TD
DTE
Null-modem
Straight
Pin3
TD
RD
DCE
Straight
Null-modem
Legend:
RD=Received data; TD=Transmitted data
Table 4-1. Pin assignments and applicable serial cables
Serial cable types
Straight serial cable
Null-modem serial cable
Straight pin-outs on both ends
Straight pin-out at the one end and
cross pin-out at the other end
(interchange lines of TX and RX)
Table 4-2. Serial cable types
4.2.2. Example connection diagrams
Following cases are examples; devices may have different receptacles and pin-outs.
Figure 4-2. Extending RS-232 between computer (DTE) and projector (DCE)
Figure 4-3. Extending RS-232 between computer (DTE) and computer (DTE)
