Serial Communication
The System 7SC can be remotely controlled via a host computer or other device (such as a control system) attached to the rear panel
The switcher uses a protocol of 9600 baud, 1 stop bit, no parity, and no flow control.
The rear panel
Pin |
| Description |
1 | – | No connection |
2 | Tx | Transmit data |
3 | Rx | Receive data |
4 | Tx 2 | Transmit data |
5 | Gnd | Signal ground |
6 | – | No connection |
7 | – | No connection |
8 | Rx 2 | Receive data |
9 | – | No connection |
51
96
DB9 Pin Locations
Female
Pins 4 and 8 on the host connector must be used for Tx2 and Rx2 only (for communicating with a slaved switcher), and not for other signals in the host system. If needed, disable or disconnect pins 4 and 8 on the host side.
RS-232 Programmer’s Guide
Host-to-switcher communications
SIS commands consist of one or more characters per field. No special characters are required to begin or end a command sequence. When the System 7SC determines that a command is valid, it executes the command and sends a response to the host device. All responses from the switcher to the host end with a carriage return and a line feed (CR/LF = 
), which signals the end of the response character string. A string is one or more characters.
Switcher-initiated messages
When a local event such as a front panel (or SCP control pad) selection or adjustment takes place, the System 7SC switcher responds by sending a message to the host. No response is required from the host. The
(C) Copyright 2001, Extron Electronics, System 7SC, Vx.xx 
The System 7SC sends the copyright message when it first powers on. Vx.xx is the firmware version number.
C hn X1
(where X1 is the input number)
The System 7SC sends this response when an input is switched. C = both audio and video were switched.
Error responses
When the switcher receives a valid SIS command, it executes the command and sends a response to the host device. If the System 7SC is unable to execute the command because the command is invalid or it contains invalid parameters, it returns an error response to the host.
The error response codes and their descriptions are as follows:
E01 – Invalid input channel number (the number is too large)
E10 – Invalid command
E13 – Invalid value (the number is out of range/too large)
E16 – Unit is busy
E23 – Checksum error.
