V.24 Standard - Aastra Ascotel IntelliGate A150 System Manual

Interfaces and Terminals as of I7.8
2. 3. 2. 1

V.24 standard

In accordance with the V.24 recommendation, a cable length of 15 m limits the
transmission speed to 38 400 bit/s. The maximum transmission speed via the V.24
interfaces on the mainboard (20x5 systems only) is 115200 bit/s. Transmission er-
rors can occur if these limits are exceeded. A current loop converter (TTY) has to be
used if the cable length is insufficient. Cable lengths of up to approx. 1 km are pos-
sible with this interface.
Two types of equipment can be connected to the V.24 interface:
• DCE: Data Communication Equipment
e. g. a PC
• DTE: Data Terminal Equipment
e. g. a printer
The pin assignment differs according to the type of equipment used. Signals are
specified as follows:
Tab. 11 V.24 signals
Pin
Signal
D-Sub-9
TXD 3
RXD 2
RTS 7
CTS 8
DTR 4
DSR 6
DCD 1
SGND 5
A straight connecting cable (modem cable; straight) must be used when connect-
ing DTE-type equipment with DCE-type equipment (e.g. PC → modem,
modem → PC).
A null modem cable must be used when connecting equipment of similar type DTE
– DTE (e. g. PC→ PC). The null modem cable is crossed.
The DCD signal should only be used if a DCE is connected with a DTE.
DCD is activated by the DCE once the connection to the DTE is established.
36
Signal direction
D-Sub-25 DTE
2 out
3 in
4 out
5 in
20 out
6 in
8 in
7 —
CCITT stand-
ard V.24
DCE
in 103
out 104
in 105
out 106
in 108
out 107
out 109
— 102
Name / function
Transmitted Data
Received Data
Request To Send
Clear To Send
Data Terminal Ready
Data Set Ready
Data Carrier Detect
Signal Ground
System Interfaces