US 7,321,788 B2
Synchronizing RF system
Kenneth L. Addy, Massapequa, N.Y. (US); and Steven J. Winick, Woodmere, N.Y. (US)
Assigned to Honeywell International, Inc., Morristown, N.J. (US)
Filed on Sep. 11, 2003, as Appl. No. 10/659,952.
Prior Publication US 2005/0059436 A1, Mar. 17, 2005
Int. Cl. H04B 1/38 (2006.01)
U.S. Cl. 455—574  [455/404.1; 340/539.3; 340/825.72; 370/315; 370/311] 8 Claims
OG exemplary drawing
 
1. A security alarm system comprising:
at least one battery powered wireless keypad comprising a Radio Frequency (RF) receiver and a reduced display module, the reduced display module providing an accurate display of the present status of the security alarm system; and
an AC powered control panel comprising a RF transmitter comprising a means for transmitting first periodic sync signals over short durations and with a periodicity such that a total of all of the first periodic sync signals over a period of one hour are equal to or less than a total of 2 second on-air time per hour, the first periodic sync signals being received and used by the RF receiver to maintain proper synchronization of the receiver with the RF transmitter during second periodic wake up windows for possible transmissions of data, and means for transmitting data during at least some of the second periodic wake up windows for the transmission of data;
wherein the receiver wakes periodically to receive first periodic sync signals which are used by the receiver to maintain the receiver properly synchronized with the transmitter during the second periodic wake up windows for possible transmissions of data from the transmitter;
wherein the receiver wakes periodically for a short duration at the start of each second periodic wake up window to receive a possible transmission of data, and if no transmission is received goes back to sleep, and if a transmission is received stays awake to receive the full transmission of data, such that the average current consumed by the battery powered receiver to wake periodically to receive the first periodic sync signals to maintain synchronization and to wake periodically to listen for the possible second periodic transmissions of data is less than the average current required to maintain the receiver awake continuously; and
wherein the transmitter and receiver each further comprise clocks, the clocks in the transmitter and receiver having no more than a 2 millisecond time shift relative to each other.