The "Silent Switch" located on the top left of the iPhone may have seemed like a good idea when it was designed, but in practice it has led to problems. Enabling the switch prevents the phone from ringing and sets the phone to vibrate-only while all other sounds function as normal. That can make it difficult to tell when the switch has accidentally been activated. Unfortunately Apple did not program a bypass for the switch, but there are third-party applications and other low-tech solutions to the silent problem.
Download the "Auto Silent" application (see Resources). The application bypasses the silent switch.
Enter the Auto Silent application.
Schedule when or if you want the phone to automatically be set to vibrate-only mode. The application silences the phone during the hours specified by the user.
For a more low-tech approach to disabling the Silent Switch use a small strip of tape to cover the switch, or a drop of glue to stick the switch in the off position. These are easy and effective solutions but may not be the prettiest.