Method and apparatus for communicating signals

1. For use in conjunction with a system for producing, at a transmitter location, time division multiplexed frames comprising a plurality of channels of information signals and framing signals, communicating said frames from the transmitter location to a receiver location, and, at the receiver location, deframing the received frames to obtain frame timing signals and a bitstream of information signals which are coupled with a plurality of operating units, a method comprising the steps of:

at said transmitter location, inserting a preselected pattern of bits in a timeslot of said information signals;

at said receiver location, detecting, in the deframed bit stream, the absence of the preselected pattern of bits, and producing a control signal in response thereto; and

producing override information signals that are coupled to said operating units when said control signal is present.

2. The method as defined by claim 1 , further comprising the step of producing, at said receiver location, auxiliary frame timing signals for use when said control signal is absent.

3. The method as defined by claim 2 , wherein said auxiliary frame timing signals are derived from the timing of the preselected pattern.

4. The method as defined by claim 1 , wherein said step of inserting said preselected pattern of bits in a timeslot of said information signals comprises inserting said preselected pattern of bits in the last timeslot of said information channels.

5. The method as defined by claim 2 , wherein said step of inserting said preselected pattern of bits in a timeslot of said information signals comprises inserting said preselected pattern of bits in the last timeslot of the said information channels.

6. The method as defined by claim 1 , wherein said step of detecting, in the deframed bit stream, the absence of the preselected pattern of bits, and producing a control signal in response thereto, includes detecting the absence of two successive occurrences of the preselected pattern of bits, and producing said control signal in response thereto.

7. The method as defined by claim 2 , wherein said step of detecting, in the deframed bit stream, the absence of the preselected pattern of bits, and producing a control signal in response thereto, includes detecting the absence of two successive occurrences of the preselected pattern of bits, and producing said control signal in response thereto.

8. The method as defined by claim 1 , wherein said time division multiplexed frames are T1 frames.

9. The method as defined by claim 2 , wherein said time division multiplexed frames are T1 frames.

10. The method as defined by claim 3 , wherein said time division multiplexed frames are T1 frames.

11. For use in conjunction with a system for producing, at a transmitter location, time division multiplexed frames comprising a plurality of channels of information signals and framing signals, communicating said frames from the transmitter location to a receiver location, and, at the receiver location, deframing the received frames to obtain frame timing signals and a bitstream of information signals which are coupled with a plurality of operating units, an apparatus, comprising: at said transmitter location, means for inserting a preselected pattern of bits in a timeslot of said information signals;

at said receiver location, means for detecting, in the deframed bit stream, the absence of the preselected pattern of bits, and for producing a control signal in response thereto; and

means for producing override information signals that are coupled to said operating units when said control signal is present.

12. Apparatus as defined by claim 11 , further comprising means for producing, at said receiver location, auxiliary frame timing signals for use when said control signal is absent.

13. Apparatus as defined by claim 12 , wherein said auxiliary frame timing signals are derived from the timing of the preselected pattern.

14. Apparatus as defined by claim 11 , wherein said means for inserting said preselected pattern of bits in a timeslot of said information signals comprises means for inserting said preselected pattern of bits in the last timeslot of said information channels.

15. Apparatus as defined by claim 12 , wherein said means for inserting said preselected pattern of bits in a timeslot of said information signals comprises means for inserting said preselected pattern of bits in the last timeslot of said information channels.

16. Apparatus as defined by claim 11 , wherein said means for detecting, in the deframed bit stream, the absence of the preselected pattern of bits, and for producing a control signal in response thereto, includes means for detecting the absence of two successive occurrences of the preselected pattern of bits, and for producing said control signal in response thereto.

17. Apparatus as defined by claim 12 , wherein said means for detecting, in the deframed bit stream, the absence of the preselected pattern of bits, and for producing a control signal in response thereto, includes means for detecting the absence of two successive occurrences of the preselected pattern of bits, and for producing said control signal in response thereto.

18. Apparatus as defined by claim 11 , wherein said time division multiplexed frames are T1 frames.

19. Apparatus as defined by claim 12 , wherein said time division multiplexed frames are T1 frames.

20. Apparatus as defined by claim 13 , wherein said time division multiplexed frames are T1 frames.