Search and response of labels in an RF ESL system

A method of optimizing (load balancing) in which a number of electronic point of purchase display units, labels, (18) are assigned to a communicator (16) in a display system (used e.g. in a retail outlet) that includes multiple communicators in communication with display units. The method includes, identifying for each display unit a preferred communicator/s based on signal strength and assigning display units to communicators. The number of display units assigned to each communicator is calculated. When the number is outside a predetermined range display units are reassigned. A method of determining the location of a plurality of electronic point of purchase display units which are in communication with a first communicator, includes of broadcasting on the first communicator a command message including instructions causing display units to broadcast a response message at a calculated time. Upon receipt of the broadcast command message at a first display unit, calculating a response time at which time the first display unit is to send the response message. The response time is based on the RF address of the display unit, and the response message comprising information identifying the first display unit and the first display unit broadcasting the response message at the calculated response time.