The Ringer Equivalency Number (REN) for the iMac modem is 0.3. This information can be obtained from the product label on the modem card itself.
The maximum REN for a home telephone system is typically 5.0. A customer should contact their local phone company to determine what their maximum REN is.
For information on Ringer Equivalency Numbers and troubleshooting, please see the following Knowledge Base article:
Article 30056: "
Modem: Not Answering Calls"