Each juror receives a jury summons. On the back of that summons is information on the time and place to report for jury duty. In addition, there is a telephone number listed for the "jury line".
Jurors must call this number, anytime after 6:00 p.m., on the evening before the service date shown on their summons. A recorded message will inform you if your appearance will be required. This message will run the entire night until normal business hours. Sometimes the court is able to release some or all of the jurors when the need for jurors is less than anticipated.