The IACM4000 is a new and more advanced version of the the Internet Alert™ 510. It solves the problem of engaged tones without the unnecessary expense of a second line and monthly rental charges. Ideal for both home and office use with a compatible PABX. Most Internet users share a single telephone line for all Internet and telephone activities. During Internet sessions, incoming calls are missed. Internet Alert Call Manager 4000™ is the cost-effective way to create a Virtual second line. Using Call Waiting and Caller Display telephone services, IACM 4000™ identifies the presence of an incoming call and displays the caller s details, giving you the option to take the second call or carry on surfing.