The 4 Position Code Activated Switch, Model 4P-MAS allows one master RS-232 port to be selectively switched to any of four RS-232 devices. Typically, the 4P-MAS is used to allow one modem to access the configuration or out-of-band management ports of four remote devices. Three modes of operation allow the selection of the port to be connected.

There are four DB25S female connectors on the rear panel for the switched ports, and one DB25P male connector for the Master Port.

The 4P-MAS also supports an internal modem option. Dataprobe supplies modems from 2400 bps to 33.6 Kbps.