This Communications Toolbox (CTB), produced by Apple, allows routing software (and other software which can use the CTB interface) to use modems and ISDN Terminal Adaptors. Also allows Macintoshes that support SerialDMA to have 115.2Kbps and 230.4Kbps connections, support of the Microcom Networking Protcol (MNP levels 1 through 4) and CCITT v.42bis data compression protocol. Unnecessary if you are not on the Internet.