Smart switches can be used to connect one RS232 port to four or more different serial devices. Smart switches are also called 'code operated switches' or 'line sharers'.
A smart switch can be controlled in two different ways.
The first way is referred to as 'smart switch mode' In this mode the switch is controlled by by sending a preamble (usually three characters) to the master port. One character of the preamble code is user programmable by internal switch settings. As soon as the preamble code is received, the slave port is connected to the master port.
The second way the switch can be controlled is referred to as 'port combiner mode' In port combiner mode, a slave port can gain access to the master port by accessing a handshake line (RTS for DTE slave ports, CTS for DCE slave ports) If none of the slave ports have their handshake lines asserted, the switch can be controlled using the preamble codes. There is no delay through these switches and the data is not buffered. LEDs indicate which port is selected.
B&B Electronics design, manufacture and distribute a complete range of smart switches.