Yawkaw,
To answer your question. It is illegal to record a conversation in 38 states in the US without the other parties consent and knowledge. That usually applies to people with tape recording devices in hand or held up to or connected to their personal phones. However, FCC rules state that to legaly record a conversation via the use of an automated system built in to the phone system, the line must have an audible "beep" or "tone" notifying the caller at least every 30 seconds. This applies even though the recording that proceeds the call says something to the effect of "This call may be monitored for quality assurance"
So, if a phone line in the US (FCC Jurusdiction) is recorded, it must have a beep or tone. If it doesn't, not only is the owner/operator in violation against FCC policy, but he/she is also breaking the law. Not to mention the fact that the recording would not be admissable in court.