Extron • System 4
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Switcher Series • User’s Manual
Appendix A • RS-232 Programmer’s Guide
A-3
Simple Instruction Set
A simple command may be a single character typed on a keyboard and does not
require any special characters before or after. (i.e. It is not necessary to press
“enter” from the keyboard.) However, some command characters may be
followed by a “delimiter” character which further defines a specific request.
Related Terms
The following terms may be helpful in understanding information in the tables
and examples that follow.
Delimiter:
A delimiter character may specify audio and not video, the switcher and not the
projector, etc. For commands that have more than one character, the delimiter is
always the last character for that command.
Line Feed/Carriage Return:
General – On most keyboards, pressing “enter” creates a line feed (lf) and a
carriage return (cr). The screen cursor moves down one line (lf) and to the left
margin (cr). This is done to prevent stringing unrelated information together.
Because these are separate functions, the programmer may send them at any
time, and in either sequence (lf/cr or cr/lf). Also, some applications may issue
these commands at the beginning of a sequence, at the end of a sequence, or
both. Each response (as seen on a terminal display) will use it in one form or
another.
System 4
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– The System 4
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uses lf/cr before and after each response and is
symbolized as
(¿)
in examples that follow.
Discrete Command:
A “discrete” command can do only one thing. For example, if projector power is
already On, sending a “discrete power on” command does nothing. See toggle.
Display, or Display Device:
“Display” refers to the video output device (projector, monitor, etc.)
Host:
Any device capable of talking to the switcher through an RS-232 port.
Space:
When writing programs, it is critical to know when to insert a space and when to
leave it out. If not done correctly, the command will not work. Examples in this
chapter use a dot (·) to represent a space. This should eliminate any confusion.
Switcher:
“Switcher” refers to the System 4
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or any slave inputs from other sources.
Terminal:
Any device that includes a keyboard and a display. This could be a “dumb”
terminal, a “smart” terminal, a PC operating in “terminal” mode, etc.
Toggle:
A “toggle” command changes the state of the function. This can be either of two
things: If the function was Off, the command turns it On; if the function was On,
the command turns it Off. A toggle command character may be either upper or
lower case.
Zero:
The number zero may be shown as Ø to distinguish it from the letter “O”.
The codes discussed in this section include any character that may be part of a
command or part of a response. This includes delimiter characters, data
characters, etc. Some functions may have more than one command. For
example, Power has a “turn on”, a “turn off” and a “toggle” command.
