Because Classic design wasn't conducive to expansion, MacTCP was bolted on to the existing system instead of being integrated. Nonetheless, MacTCP does work well, and it requires very little memory. This is Apple's new modular and extendable networking system that's integrated into System 7.6 and higher. But note that this networking system requires quite a bit of memory. Modem Initialization String.
All modern modems can take commands that affect their configuration.
These commands include the ability to turn off the modem's speaker or set its volume and information relevant to connecting with other modems. For example, fax modems require one initialization string to tell the modem to do fax, and another to do data. This is a modem description file used by several popular dialers. Among other settings, the CCL contains the modem initialization string. While ARA 2 and ARA 3 both use CCLs, the ARA 2 CCLs are not necessarily compatible with ARA 3 and vice versa.