1. Plural of callboard; boards or bulletin boards in a theater where notices, schedules, and cast information are posted for actors and crew.
Usage: theater/performing arts; typically plural in usage
2. In telecommunications and switchboard operations, boards or systems used to display incoming calls or connect callers; call management displays.
Usage: technical; dated/historical

Examples

• The stage manager posted the rehearsal schedule on the callboards.
• Actors checked the callboards every morning to see their call times.
• The theater's callboards displayed emergency contact information for the cast.
• Before smartphones, telephone operators used callboards to manage incoming lines.
• The director's notes were pinned to the callboards in the green room.