Caller ID Service
CallerRM works with your phone company's caller ID service, contact them if they are not providing you with this service yet. Usually the caller ID information is sent between the first and second rings. So do not pick up your phone too early when you receive a call, otherwise the information may be lost.

Modem
You will need a modem that supports caller ID; either internal or external are OK. Some computers already have internal modems installed.
To test if your modem supports caller ID, open the program "HyperTerminal", try these commands:
AT+VCID=1
AT#CID=1
AT%CCID=1
AT#CC1
AT*ID1
Your modem should return "OK" to at least one of the commands.