Transmit control system using in-band tone signalling

• US 5,896,560 A
• Filed: 04/12/1996
• Issued: 04/20/1999
• Est. Priority Date: 04/12/1996
• Status: Expired due to Term

• Current Assignee: E F Johnson Company (JVC Kenwood Corporation)
• Original Assignee: Transcrypt Internationall E F Johnson Company
• Inventors: Bauman, Donald R., Pfiefer, Steve, Lyon, James K.
• Primary Examiner(s): Vo, Nguyen
• Assistant Examiner(s): Bhattacharya, Sam
• Application Number:
  US08/631,866
• Time in Patent Office: 1,103 Days
• Field of Search: 455/33.1, 455/54.1, 455/56.1, 455/58.2, 455/57.1, 455/68, 455/35.1, 455/36.1, 455/37.1, 455/38.2, 455/38.5, 455/32.1, 455/509, 455/515, 455/517, 455/518 , 455/521, 455/526, 455/528, 379/59, 379/60, 379/283, 379/351, 379/386
• US Class Current: 455/701
• CPC Class Codes: H04B 1/60 Supervising unattended repeaters
• CPC Class Codes: H04H 20/67 Common-wave systems, i.e. using separate transmitters operating on substantially the same frequency
• CPC Class Codes: H04L 12/12 Arrangements for remote connection or disconnection of substations or of equipment thereof
• CPC Class Codes: H04W 84/08 Trunked mobile radio systems

Abstract

A transmit control system using in-band tones for activating and deactivating one or more remote sites. The transmit control system detecting energy in two or more spectral regions to determine if the signal received is a harmonic signal or a signalling tone to prevent accidental deactivation of the transmitter system. In one application, a modified Goertzel algorithm is employed by a digital signal processor to provide tone detection and a two stage detection provides controlled switching in noisy environments.

Claims

1. A method for transmit control in a repeater system, comprising the steps of:

transmitting an in-band tone of frequency F when a central site has no information to transmit over one or more remote sites, and inhibiting the in-band tone when the central site has information to transmit over the one or more remote sites; and

at each of the one or more remote sites, controlling a transmitter, by the steps including;

analog to digital converting the in-band tone to create a digitized in-band tone;

detecting the digitized in-band tone using a processor;

if the in-band tone is detected and if measured signals from a different spectral region are substantially absent, disabling a transmitter at the remote site; and

if no in-band tone is detected, activating the transmitter.

2. The method of claim 1, wherein the different spectral region is a data spectral region.

3. The method of claim 1, wherein the different spectral region is a voice spectral region.

4. The method of claim 1, wherein the step of detecting comprises the step of using a modified Goertzel measurement system to detect the in-band tone.

5. The method of claim 1, wherein the step of transmitting further comprises the step of transmitting a 2600 Hz in-band tone.

6. A method for transmit control in a repeater system, comprising the steps of:

analog to digital converting an in-band tone to create a digitized in-band tone;

detecting the digitized in-band tone using a processor, the in-band tone transmitted by a central site when the central site has no information to transmit over one or more remote sites and the in-band tone inhibited when the central site has information to transmit over the one or more remote sites;

if the in-band tone is detected, measuring signals from a different spectral region, if signals from the different spectral region are substantially absent, then disabling a transmitter at a remote site; and

if no in-band tone is detected, activating the transmitter.

7. The method of claim 6, wherein the different spectral region is a data spectral region.

8. The method of claim 6, wherein the different spectral region is a voice spectral region.

9. The method of claim 6, wherein the step of detecting comprises the step of using a modified Goertzel measurement system to detect the in-band tone.

10. The method of claim 6, wherein the in-band tone is a 2600 Hz in-band tone.

11. A method for transmit control in a repeater system, comprising the steps of:

transmitting an in-band tone of frequency F when a central site has no information to transmit over one or more remote sites, and inhibiting the in-band tone when the central site has information to transmit over the one or more remote sites, wherein the in-band tone is for analog to digital conversion and detection at a remote site, and if the in-band tone is detected and if signals from a different spectral region are substantially absent, disabling a transmitter at the remote site.

12. The method of claim 11, wherein the different spectral region is a data spectral region.

13. The method of claim 11, wherein the different spectral region is a voice spectral region.

14. The method of claim 11, wherein a modified Goertzel measurement system is used to detect the in-band tone.

15. The method of claim 11, wherein the step of transmitting further comprises the step of transmitting a 2600 Hz in-band tone.

16. A transmit control system, comprising:

an in-band tone generator for generating an in-band tone when a central site has no information to transmit;

an analog to digital convertor for converting signals in a spectral vicinity of the in-band tone;

a processor, located at a remote site, for detecting an in-band tone from samples generated by the analog to digital convertor; and

a comparator for comparing signals generated by the analog to digital convertor and signals from a different spectral area.

17. The system of claim 16, further comprising a transmission inhibitor for disabling a transmitter at the remote site if an in-band tone is detected and energy in a different spectral region is not detected.

18. The system of claim 16, wherein the processor executes a modified Goertzel algorithm for detecting an in-band tone signal.

19. The system of claim 16, wherein the in-band tone generator generates a 2600 Hz tone.

20. The system of claim 16, wherein the signals from a different spectral area comprise data signals transmitted by the central site.

21. A method of link detection, comprising:

monitoring signals from a central site, including monitoring a predetermined spectral region for presence of an in-band tone;

if an in-band tone is detected, signalling an active link; and

if the in-band tone is not detected and if wideband spectral energy is substantially absent over an interval of time, signalling an inactive link;

wherein the interval of time is selected to avoid errors in detection during fluctuation of signals from the central site.