Stan's Notebook: Connect up to 17 devices to one serial port

Often called “line sharers” or “code-activated switches,” B&B Electronics’ smart switches can be used to connect one RS-232 port to four or more different serial devices. These switches 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 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 selected 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 asserting a handshake line (RTS for DTE slave ports, CTS for DCE slave ports). If none of the slave ports have their handshake line asserted, the switch can be controlled using the preamble codes. There is no delay through non-buffered switches. LEDs indicate which port is selected.

Marcus' Notebook: Connect up to 17 devices to one serial port

Often called “line sharers” or “code-activated switches,” B&B Electronics’ smart switches can be used to connect one RS-232 port to four or more different serial devices. These switches 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 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 selected 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 asserting a handshake line (RTS for DTE slave ports, CTS for DCE slave ports). If none of the slave ports have their handshake line asserted, the switch can be controlled using the preamble codes. There is no delay through non-buffered switches. LEDs indicate which port is selected.