VISUAL 100 - Table 2-1 EIA RS232-C Signal Definitions and Connector Pins, and 20 MA Current Loop Pin Polarity

Pin
1
2
3
4
5
6
7
8
11
12
17
18
19
20
21
23*
25
VISUAL TECHNOLOGY INCORPORATED, 540 MAIN STREET, TEWKSBURY, MA 01876
The VISUAL 100 provides as standard, both an EIA RS232-C and a 20-milliampere current
loop interface. Both interfaces conform to a bit-serial, asynchronous, start-stop format and
operate in a full-duplex mode.
The EIA RS232-C interface provides all control and sequencing signals for interfacing to
remote equipment through a modem or for direct connection to local equipment. This
interface labeled EIA, is located on the rear panel and interfaces with the communication
line via a 25 pin connector. Table 2-1 lists all the EIA signal definitions and connector pins
for the RS232-C interface.
The 20-milliampere current loop interface may be passive or active and allows direct connec-
tion to most equipment. Table 2-1 lists the pin polarity designations for the 20-milliampere
current loop interface.
TABLE 2-1
EIA RS232-C SIGNAL DEFINITIONS AND CONNECTOR PINS,
AND 20 MA CURRENT LOOP PIN POLARITY
RS232-C CCITT V24
Mnemonic Mnemonic Definition
AA 101
Protective Ground
BA 103
Transmit Data to Modem
BB 104 Receive Data from Modem
CA 105
Request-to-Send
CB
106
Clear-to-Send
cc
107 Data Set Ready
AB 102
Signal Ground
CF 109
Carrier Detect
SCA
-
Secondary Channel Request-to-Send (202 modem)
SCF 122
Secondary Channel Carrier Detect
- - Current Loop Receive -
- - Current Loop Receive +
SCA 120
Secondary Channel Request-to-Send ( RS232, V24 modem)
CD 108.2
Data Terminal Ready
-
- Current Loop Transmit +
CH 111
Speed Select, always ON (High Speed)
- -
Current Loop Transmit -
*Pin 23 is used on some dual-speed modems to select speed. This VISUAL 100 always has this signal ON.
If low speed operation of the dual-speed modem is desired, it is necessary to "float" pin 23 (extract pin 23
from the modem cable at one end).
4