Patent ID: 7212117

Claim:
Apparatus for wireless synchronization of electronic article surveillance systems, reducing the need for manual adjustment of transmitter timing by continually adapting and updating timing automatically to changing environmental conditions, comprising: a first phase locked loop including: means, responsive to a power line zero crossing, for detecting a line phase error; a first numerically controlled oscillator responsive to said line phase error and to a crystal oscillator, said first numerically controlled oscillator and having a reference output, said reference output being an input to said line phase error means; and, a second phase locked loop including: means, responsive to a transmit signal from a first electronic article surveillance system, for detecting a transmit phase error; and, a second numerically controlled oscillator responsive to said transmit phase error and said reference output; said second numerically controlled oscillator having a synchronized transmit output, said synchronized transmit output being an input to said transmit phase error means; and, wherein said synchronized transmit output being usable as a trigger for synchronized transmission of a second electronic article surveillance system.