A Caller ID telephone device is shown, which can identify the caller of a telephone call in either the on-hook or off-hook states. The CID telephone device includes a circuit for detecting a CPE alerting signal, a circuit for generating an acknowledgment signal when the CPE alerting signal is detected,...http://www.google.de/patents/US5970128?utm_source=gb-gplus-sharePatent US5970128 - Telephone device for caller identification
