User`s guide

SWITCHERS
10
plugging the unit back in (power on).
7.2 RS-232 CONTROL
The MX2222AT Switcher offers remote control
capabilities through RS-232; the primary
communications standard used by control systems
and computers.
In fact, the MX2222AT offers more features using
RS-232 than are currently available from the front
panel of the unit.
The MX2222AT offers a terminal block using
solder-free, screw-down contacts, making it
extremely easy to connect the switcher to a control
system or a computer in the field.
RS-232 Terminal Block
PIN No. PIN Designation
1 +5V (not needed for
RS-232 connection)
2 GND (Ground)
3 RCV (Receive)
4 XMT (Transmit)
The terminal block is labeled with the proper
contact designations: Transmit (XMT), Receive
(RCV), and Ground (GND). Always remember that
the Transmit pin from the control system or
computer must be connected to the Receive pin on
the switcher control port; do not connect Transmit
to Transmit or Receive to Receive.
Note: the contact labeled +5V is not used for
RS-232 connections. This contact is used
for providing DC voltage to other equipment
installed within close proximity of the
MX2222AT.
Typically, a control system or computer will offer
RS-232 connections on a 9-pin D connector.
The following are typical cable pin-out designations
for RS-232 connections on a 9-pin D connector.
Always verify that the pin-outs for your system are
correct to ensure the proper wiring.
IBM PIN No.
MX2222AT Contact
3 RX
2 TX
7 GND
Connection of IBM-PC 25-pin D to the MX2222AT
Terminal Block
IBM PIN No.
MX2222AT Contact
2 TX
3 RX
5 GND
Connection of IBM-PC 9-pin D to the MX2222AT
Terminal Block
The MX2222AT has two LEDs on either side of the
control port terminal block connector. These LEDs
are used to determine that a proper connection has
been made. If both LEDs turn green, the
connection is correct.
Port setting preferences for the control system or
computer being used to control the switcher should
be set as follows:
BAUD RATE (Bits per second) 2400
Data bits 8
Parity None
Stop Bits 1
There is no software or hardware flow control
implemented. The RS-232 input has a 6-character
buffer and will not execute additional commands
until the previous command is fully processed.