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A low-power RF receiver has a decreased current consumption. The receiver may be used in control devices, such as battery-powered motorized window treatments and two-wire dimmer switches. The receiver uses an RF sub-sampling technique to check for RF signals and then puts the receiver to sleep for a

A low-power RF receiver has a decreased current consumption. The receiver may be used in control devices, such as battery-powered motorized window treatments and two-wire dimmer switches. The receiver uses an RF sub-sampling technique to check for RF signals and then puts the receiver to sleep for a sleep time that is longer than a packet length of a transmitted packet to conserve battery power. The receiver compares detected RF energy to a threshold that may be increased to decrease the sensitivity of the receiver and increase the battery lifetime. After detecting an RF signal, the receiver is put to sleep for a snooze time that is longer than the sleep time and just slightly shorter than the time between two consecutive transmitted packets.

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1. A load control device for controlling an electrical load receiving power from a power source in response to RF signals transmitted by an RF transmitter, the RF transmitter adapted to transmit a predetermined number of consecutive packets at a predetermined transmission rate during a given transmi

1. A load control device for controlling an electrical load receiving power from a power source in response to RF signals transmitted by an RF transmitter, the RF transmitter adapted to transmit a predetermined number of consecutive packets at a predetermined transmission rate during a given transmission event, each of the packets including a same command and characterized by a packet length, the load control device comprising: an RF receiver adapted to receive packets from the RF transmitter, the RF receiver operable to be periodically enabled for a sample time period to determine if the RF transmitter is transmitting one of the consecutive packets, the RF receiver operable to enter a sleep mode for a sleep time period between consecutive sample time periods if the RF receiver determines that the RF transmitter is not transmitting one of the consecutive packets during the sample time period; anda controller operatively coupled to the RF receiver, the controller operable to determine that the RF transmitter is transmitting one of the consecutive packets during the sample time period and to subsequently receive an entire packet of the consecutive packets, the controller operable to control the electrical load in response to the entire packet received from the RF transmitter;wherein the sleep time period of the RF receiver is longer than the packet length of each of the packets, the sample time period of the RF receiver is less than the packet length, and the sample time period and the sleep time period between sample time periods are sized to ensure that the sample time period coincides with at least one packet of the predetermined number of consecutive packets in the transmission event. 2. The load control device of claim 1, wherein: the controller and the RF receiver are operable to be powered by a battery. 3. The load control device of claim 2, wherein the controller can be controlled into a sleep mode in which the controller consumes less power than in a normal mode. 4. The load control device of claim 3, wherein the RF receiver is operable to determine if detected RF energy exceeds a detect threshold, the RF receiver operable to wake up the controller from the sleep mode to enter the normal mode in response to determining that the detected RF energy exceeds the detect threshold. 5. The load control device of claim 4, wherein the controller is operable to put the RF receiver and the controller to sleep for a snooze time in response to determining that the detected RF energy exceeds the detect threshold, the RF receiver and the controller operable to wake up after the snooze time such that the controller is operable to receive one of the consecutive packets. 6. The load control device of claim 5, wherein the snooze time is slightly less than a break time between two subsequent ones of the consecutive packets. 7. The load control device of claim 4, wherein the controller is operable to adjust the detect threshold of the RF receiver, wherein the detect threshold can be increased to prevent noise signals from causing the RF receiver to wake up the controller thereby conserving battery power. 8. The load control device of claim 7, wherein the controller is operable to adjust the detect threshold from an extended range threshold close to a noise floor to an extended battery mode threshold greater than the extended range threshold. 9. The load control device of claim 2, wherein the electrical load comprises a motor for adjusting a covering material of a motorized window treatment, the load control device comprising: a motor drive circuit coupled to the motor for driving the motor to thus open and close the covering material. 10. The load control device of claim 9, further comprising: a drive shaft; andat least one lift cord rotatably received around the drive shaft and extending to a bottom of the covering material for raising and lowering the covering material;wherein the motor is operatively coupled to the drive shaft such that the motor is operable to raise and lower the covering material by rotating the drive shaft. 11. The load control device of claim 2, further comprising: at least one visual indicator operable to display an indication of a state of the load. 12. The load control device of claim 11, wherein the load control device comprises a battery-powered remote control. 13. The load control device of claim 2, wherein the load control device comprises a temperature control device operable to control a heating and/or cooling system in response to the entire packet received from the RF transmitter. 14. The load control device of claim 1, further comprising: a controllably conductive device adapted to be coupled in series electrical connection between the power source and the electrical load for controlling the power delivered to the electrical load;wherein the controller is operatively coupled to a control input of the controllably conductive device for controlling the power delivered to the electrical load in response to the entire packet received from the RF transmitter. 15. The load control device of claim 14, further comprising: a power supply coupled in parallel electrical connection with the controllably conductive device, the power supply operable to conduct a charging current through the electrical load in order to generate a DC supply voltage for powering the controller. 16. The load control device of claim 14, further comprising: a ground terminal adapted to be coupled to earth ground; anda power supply adapted to conduct a charging current through the ground terminal in order to generate a DC supply voltage for powering the controller. 17. The load control device of claim 14, wherein the electrical load comprises a lighting load and the load control device comprises a dimmer switch for controlling an amount of power delivered to the lighting load to adjust an intensity of the lighting load. 18. The load control device of claim 1, wherein a packet break time period exists between any two consecutive packets. 19. An RF communication system comprising: an RF transmitter adapted to transmit a predetermined number of consecutive packets at a predetermined transmission rate during a given transmission event, each of the packets including a same command and characterized by a packet length; andan RF receiver adapted to receive packets from the RF transmitter, the RF receiver operable to be periodically enabled for a sampling time to determine if the RF transmitter is transmitting one of the consecutive packets, the RF receiver operable to enter a sleep mode for a sleep time period between consecutive sample time periods if the RF receiver determines that the RF transmitter is not transmitting one of the consecutive packets during the sample time period;wherein, if the RF transmitter is transmitting one of the consecutive packets during the sample time period, the RF transmitter is operable to be enabled to subsequently receive an entire packet of the consecutive packets; andwherein the sleep time period of the RF receiver is longer than the packet length of each of the packets, the sampling time of the RF receiver is less than the packet length, and the sampling time and the sleep time period between sampling times are sized to ensure that the sampling time coincides with at least one packet of the predetermined number of consecutive packets in the transmission event. 20. The RF communication system of claim 19, further comprising: a plurality of control devices operable to transmit RF signals transmitted on a first frequency. 21. The RF communication system of claim 20, further comprising: a signal repeater operable to receive a first RF signal transmitted on the first frequency by one of the control devices, the signal repeater operable to determine that the first RF signal is intended for the RF receiver, the signal repeater operable to change transmission frequencies and transmit a second RF signal related to the first RF signal to the RF receiver on a second frequency different than the first frequency. 22. The RF communication system of claim 21, wherein the signal repeater is operable to determine a number of the plurality of control devices, and to transmit the second RF signal to the RF receiver on the second frequency only if the number of control devices exceeds a threshold amount. 23. The RF communication system of claim 20, further comprising: a first signal repeater operable to receive a first RF signal transmitted on the first frequency by one of the control devices; anda second signal repeater adapted to be coupled to the first signal repeater via a communication link;wherein the first signal repeater is operable to transmit a packet to the second signal repeater via the communication link in response to receiving the first RF signal, the second signal repeater operable to transmit a second RF signal to the RF receiver on a second frequency different than the first frequency in response to receiving the packet from the first signal repeater via the communication link. 24. The RF communication system of claim 23, wherein the communication link comprises a wired communication link. 25. The RF communication system of claim 20, wherein the RF transmitter is operable to transmit the consecutive packets to the RF receiver on a second frequency different than the first frequency. 26. The RF communication system of claim 19, wherein the RF receiver comprises a battery for powering the RF receiver. 27. The RF communication system of claim 26, wherein the RF receiver comprises a battery-powered motorized window treatment for adjusting a position of a covering material. 28. The RF communication system of claim 26, wherein the RF receiver comprises a battery-powered remote control having a visual indicator. 29. The RF communication system of claim 26, wherein the RF receiver comprises a temperature control device operable to control a heating and/or cooling system. 30. The RF communication system of claim 19, wherein the RF receiver comprises a load control device adapted to be coupled in series electrical connection between an AC power source and an electrical load for controlling an amount of power delivered to the electrical load. 31. The RF communication system of claim 30, wherein the load control device comprises a two-wire device adapted to be coupled in series electrical connection between the AC power source and the electrical load without a connection to a neutral side of the AC power source. 32. The RF communication system of claim 30, wherein the load control device comprises a ground terminal adapted to be coupled to earth ground, the load control device operable to conduct a charging current for an internal power supply through the ground terminal. 33. The RF communication system of claim 19, wherein the RF transmitter comprises at least one of a battery-powered remote control, an occupancy sensor, a vacancy sensor, a daylight sensor, a temperature sensor, a humidity sensor, a security sensor, a proximity sensor, a keypad, a key fob, a cell phone, a smart phone, a tablet, a personal digital assistant, a personal computer, a timeclock, an audio-visual control, a safety device, and a central control transmitter. 34. The RF communication system of claim 19, wherein a packet break time period exists between any two consecutive packets. 35. A wireless signal receiver comprising: a wireless receiver circuit for detecting transmitted signals transmitted in a predetermined number of consecutive packets during a given transmission event, where each packet comprises a same data, there being a packet time and a time between packets longer than the packet time; anda control circuit operable to turn on the wireless receiver circuit for an on-time, the on-time being less than an off-time of the wireless receiver circuit, the on-time of the wireless receiver circuit being less than the packet time, the off-time between on-times being less than the time between packets and the off-time being longer than the packet time, the control circuit operable to determine that the wireless receiver circuit is receiving one of the consecutive packets during the on-time and to subsequently receive an entire packet of the consecutive packets;wherein the off-time and the on-time are selected so that within the plurality of packets, the on-time will coincide with the packet time to ensure that the wireless receiver circuit detects at least one packet during the transmission of the predetermined number of packets if packets are being transmitted. 36. The wireless signal receiver of claim 35, wherein the wireless receiver circuit comprises an RF receiver circuit. 37. The wireless signal receiver of claim 36, further comprising: an antenna coupled to the RF receiver circuit; anda filter circuit comprising a SAW filter coupled between the antenna and the RF receiver circuit and operable to filter out frequencies outside of a defined frequency range;wherein said RF receiver circuit is operable to remain on if an RF signal is detected, and said filter circuit is operable to prevent said RF receiver circuit from remaining on or turning on again for RF signals outside of said the defined frequency range, thereby conserving battery power. 38. The wireless signal receiver of claim 37, wherein the RF receiver circuit is operable to turn on a control circuit in response to detecting the RF signal. 39. The wireless signal receiver of claim 35, wherein the on-time is approximately 0.1 msec, the off-time is approximately 40 msec, the packet time is approximately 5 msec and the time between packets is approximately 75 msec. 40. The wireless signal receiver of claim 39, wherein the predetermined number of packets comprises twelve. 41. The wireless signal receiver of claim 35, further wherein the wireless receiver circuit is battery powered and further comprising an adaptive circuit operable to change the off-time of said wireless receiver circuit. 42. A method of communicating in a load control system, the method comprising: transmitting by an RF transmitter during a given transmission event a predetermined number of consecutive packets at a predetermined transmission rate, each of the packets including a same command and characterized by a packet length;periodically enabling an RF receiver for a sample time period to determine if the RF transmitter is transmitting one of the packets;if the RF transmitter is not transmitting one of the consecutive packets during the sample time period, putting the RF receiver in a sleep mode for a sleep time period between consecutive sample time periods; andif the RF transmitter is transmitting one of the consecutive packets during the sample time period, enabling the RF receiver to subsequently receive an entire packet of the consecutive packets;wherein the sleep time period of the RF receiver is longer than the packet length of each of the packets, the sample time period of the RF receiver is less than the packet length, and the sample time period and the sleep time period between sample time periods are sized to ensure that the sample time period coincides with at least one packet of the predetermined number of consecutive packets in the transmission event. 43. The method of claim 42, further comprising: the RF receiver determining if detected RF energy exceeds a detect threshold; andthe RF receiver waking up a controller from a sleep mode to enter a normal mode in response to determining that the detected RF energy exceeds the detect threshold. 44. The method of claim 43, further comprising: the controller putting the RF receiver and the controller to sleep for a snooze time in response to determining that the detected RF energy exceeds the detect threshold;the RF receiver and the controller waking up after the snooze time, the snooze time less than a break time between two subsequent ones of the consecutive packets; andthe controller subsequently receiving the entire packet transmitted by the RF transmitter. 45. The method of claim 44, further comprising: the controller controlling an amount of power delivered to an electrical load in response to the entire packet received from the RF transmitter. 46. The method of claim 43, further comprising: the controller adjusting the detect threshold of the RF receiver whereby the detect threshold can be increased to prevent noise signals from causing the RF receiver to wake up the controller thereby conserving battery power. 47. The method of claim 42, wherein a packet break time period exists between any two consecutive packets. 48. A wireless signal receiver circuit for detecting wireless control signals and having an on/off operation to conserve power comprising: a control circuit;a wireless receiver having an on state when it consumes power and an off state when it consumes less power than consumed in the on state, the on state having a duration substantially shorter than the off state, whereby the wireless receiver receives wireless control signals during the on state to be processed by the control circuit, the wireless control signals being sent in packets with a packet time such that there is a predefined time between packets; andwherein the wireless receiver is operable to periodically be in the on state for a sample time substantially less than the packet time to detect a wireless control signal, whereby upon detecting a first packet during the sample time, the wireless receiver is operable to enter the off state to conserve power for an amount of time slightly less than the predefined time between packets, to subsequently turn on and remain on until a succeeding packet starts to be received, and to turn off after the succeeding packet is fully received. 49. The wireless signal receiver circuit of claim 48, wherein the control circuit has an on state when it consumes power and an off state when it consumes less power than consumed in the on state, the wireless receiver operable to cause the control circuit to enter the on state in response to detecting the wireless control signals. 50. The wireless signal receiver circuit of claim 49, wherein upon the wireless receiver detecting the first packet, the control circuit is operable to determine that the wireless receiver did not receive the first packet in its entirety. 51. The wireless signal receiver circuit of claim 50, wherein upon the control circuit determining that the wireless receiver did not receive the first packet in its entirety, the control circuit is operable to cause the wireless receiver to enter the off state and to enter the off state itself to conserve power for an amount of time slightly less than the predefined time between packets. 52. The wireless signal receiver circuit of claim 48, wherein the wireless control signals are RF signals. 53. The wireless signal receiver circuit of claim 48, wherein the control circuit comprises a microprocessor. 54. The wireless signal receiver circuit of claim 48, wherein if the wireless receiver does not detect a wireless signal during the on state, the wireless receiver turns off until a next on state. 55. A system for conserving battery power of a battery powered wireless signal receiver comprising: a wireless signal receiver that periodically turns on to determine if a wireless signal is being transmitted, the wireless signal receiver being capable of receiving on any of multiple channels, the wireless signal receiver including a control circuit that determines if the wireless signal is intended for the wireless signal receiver; anda transceiver circuit for retransmitting said wireless signals, the transceiver circuit determining a number of transmitted wireless signals, and if the number exceeds a threshold amount, said transceiver circuit communicating with the wireless signal receiver to change the channel of communication to an alternate channel and retransmitting wireless signals intended for the wireless signal receiver on the alternate channel, whereby the wireless signal receiver will receive fewer wireless signals on the alternate channel, thereby remaining on for less time and reducing battery power consumption. 56. The system of claim 55, wherein the transceiver comprises a repeater for retransmitting the wireless signals from a plurality of transmitting devices. 57. The system of claim 56, wherein the repeater automatically switches to a less used alternate channel when the threshold amount is exceeded. 58. The system of claim 56, wherein the plurality of transmitting devices include at least one transmitter for controlling a battery powered motorized window treatment. 59. The system of claim 56, wherein the multiple channels have different carrier frequencies. 60. The system of claim 55, wherein the wireless signals are RF signals.