Method and apparatus for synchronizing and controlling remote receiver

• US 5,818,814 A
• Filed: 10/25/1996
• Issued: 10/06/1998
• Est. Priority Date: 10/25/1996
• Status: Expired due to Fees

• Current Assignee: IMAX Corporation
• Original Assignee: Sonics Associates, Incorporated (IMAX Corporation)
• Inventors: Testani, Alan John, Eighmy, Eugene Arnold, Edwards, William Thomas
• Primary Examiner(s): Pham, Chi H.
• Assistant Examiner(s): NGO, RICKY QUOC
• Application Number:
  US08/738,227
• Time in Patent Office: 711 Days
• Field of Search: 370/328, 370/331, 370/332, 370/212, 370/503, 455/422, 455/434, 455/436, 455/437, 455/439, 455/443, 455/39, 455/67.1, 455/68, 455/70, 455/502, 455/503, 381/77, 381/78, 381/79, 375/238, 375/316, 375/356
• US Class Current: 370/212
• CPC Class Codes: H04B 10/114 Indoor or close-range type systems
• CPC Class Codes: H04B 10/1141 One-way transmission
• CPC Class Codes: H04J 3/0614 the synchronising signal being characterised by the amplitude, duration or polarity

Abstract

A user headset is provided that is operable to contain an audio device (50) and a receiver (52). The receiver (52) is operable to receive both audio information on multiple channels and also data. The data is received in the form of pulse width modulated sync signals. The sync signals are operable to provide a synchronization signal for 3-D liquid crystal lenses (60). The data is encoded within the sync signal through pulse width modulation. The width of the pulse defines various commands. These various commands define the channel over which the audio is to be transmitted. These channels can either be user-defined or they can be a function of the transmitter. The transmitter includes an audio generator (42) for generating audio signals on multiple channels and also a data generator (40). These are modulated onto a broad band optical signal and transmitted via an IR data link. The system facilitates a walking tour by transmitting commands to the receiver that allow the receiver to lock onto a particular channel, there being select channels for a given zone. When walking from one zone to another zone, different channels in the next zone are automatically detected. The system detects the crossing of a boundary between zones by a change in sync frequency. Since the sync signals for both zones are synchronized, this facilitates a seamless transfer between adjacent zones. The synchronization is provided by transmitting a pulse stream at different frequencies with the command information encoded within the pulses by pulse-width modulation. The frequencies are harmonics of a fundamental frequency, such that the higher frequency merely adds a pulse to the pulse stream. By selecting the smallest pulse width, the highest priority transmitter can have information extracted therefrom.

Claims

1. A method for synchronizing a mobile receiver to one of a plurality of transmitters, each transmitter disposed in a separate zone and having a defined range, comprising:

providing a common command channel;

transmitting from each of the transmitters over the common command channel a carrier having a pulse stream at a frequency that is a harmonic of a predetermined fundamental frequency, the pulse streams for each of the transmitters synchronized with each other, at least two of the transmitters having different frequencies;

pulse width modulating the pulses of each of the pulse streams with command information associated with the associated transmitter;

extracting the pulse stream at the mobile receiver that was transmitted over the command channel such that, if the pulse stream received by the mobile receiver from the command channel is the result of two received transmissions from two different transmitters, the pulse edges of the two simultaneously received transmissions will be aligned;

decoding at the mobile receiver the command information in the pulse width of the highest frequency pulse stream in the event more than one transmission is received; and

executing the decoded command.

2. The method of claim 1, wherein at least two of the separate zones overlap and the transmissions of the transmitters in the two overlapping separate zones have different frequencies of transmission.

3. The method of claim 2, wherein the step of decoding comprises the step of measuring the pulse width of received ones of the pulses and determining the pulse width of the highest priority one of the transmissions if more than one pulse width is present.

4. The method of claim 3, wherein the shortest pulse width is the highest priority when more than one pulse width is received.

5. The method of claim 1, wherein different transmissions are given different priorities, with the highest priority associated with the highest frequency one of the transmitters.

6. The method of claim 1, wherein at least one of the transmitters transmits at the fundamental frequency.

7. The method of claim 6, wherein at least one of the transmitters transmits at a frequency that is twice the fundamental frequency.

8. The method of claim 7, wherein only two frequencies are present, the fundamental frequency and the frequency at twice the fundamental frequency.