5.12 RS-232 Control
There is yet one more way to select channels on the ServSwitch Duo: through its RS-232 serial port. (This is a proprietarily pinned DB15 connector; see Section A.3 of the Appendix for more information.) The normal use of this connector is as the attachment point for the Switch’s optional Remote-Control Module, but by using an adapter you can connect a different RS-232 device to it. To select a channel through this port, the data rate and format of the sending device must be set to 1200 bps, 8 data bits, no parity, and 1 stop bit. No handshaking (flow control) is used by the ServSwitch Duo.
Simply send the ASCII character for the channel which needs to be selected: ASCII “1” (31 hex, 49 decimal) will select channel 1, ASCII “2” (32 hex,
50 decimal) will select channel 2, and so on. You can select ports 10, 11, 12, 13, 14, 15, and 16 by sending the ASCII characters “A,” “B,” “C,” “D,” “E,” “F,” and “G” respectively.
5.13 Cascading ServSwitch Duos
Multiple ServSwitch Duos can be cascaded (connected together in a one-to-many scheme) in order to increase the maximum number of available CPU ports in your KVM-switching system. This can be particularly useful where clusters of computers are located some distance from each other, because each Switch unit acts as a kind of signal booster or repeater and can be as much as 100 feet (30 m) away from the other Switches in the system. To select channels in cascaded systems, you will need to either send hotkey commands from the master Switch’s keyboard (see the “{Hotkeys} + {Channel Address}” paragraph in Section 5.7) or select your desired channel from the Switch’s on-screen menu (see Section 5.8). Most people find using the menu more convenient, because scrolling through and selecting computer names from the menu is usually much easier than trying to remember and type in channel addresses.
Though it’s theoreticallly possible to cascade ServSwitch Duos to four, five, or more “layers,” we recommend that you limit your setup to three, because the channel addresses for CPU ports on Switches beyond the third layer are too long to be entered in the menu.
