An Apple patent application has been filed that provides for a dynamic warning of an impending dropped cell phone call. The filing describes a technique to give the caller a warning of how much time they have left before the call is dropped.

The U.S. Patent and Trademark Office filing was made on November 27, 2006 and posted by the USPO on Friday.

The filing by Michael M. Lee et al says, in part, "In order to provide notice of poor signal quality, some wireless devices have a one-way signal strength indicator that is a rough estimator of quality of the radio frequency signal between the covering base station and the receiving wireless device. For example, U.S. Pat. No. 5,809,414 to Coverdale et al. selectively provides to a user a signal strength indication using one or more pre-selected criteria.

"Unfortunately, however, this signal strength indicator provides the user with an indication of the signal quality only at that particular moment in time which is usually too late to take corrective measures in order to avoid the lost wireless signal or at least mitigate the effects of the lost signal when, or if, it occurs."

In one of the embodiments, an out of range warning can provide the user with an estimate of time before the signal is lost and possible corrective action. Warnings can take the form of a vibration, or audible and visual warnings.

The projected "out of range" condition could happen if, for example, the caller is in a moving vehicle. A warning could alert the caller to pull over to avoid going out of signal range. In addition, the patent discusses the conditions under which the warning is issued, for example only when it would affect a call in the "here and now." In addition, the patent filing proposes that the "warning can be wirelessly transmitted to any other person currently in communication with the user of the wireless device indicating that the call may be dropped."

Hopefully, there wonit be a rash of rear-end collisions some day as iPhone users in cars hit their brakes to avoid a lost signal.