Overvoltage protector circuit and a detector circuit for supervising such a protector circuit

1. An overvoltage protector circuit for telecommunication equipments, said protector circuit including a gas discharge tube connected to a communication line for passing any harmful surge currents appearing in the line to the ground, wherein a degradation detector circuit is arranged to detect any degradation of the gas discharge tube, the detector circuit comprises a reference gas discharge tube with a higher breakdown voltage than the supervised gas discharge tube and an alarm circuit loop connected to an alarm system, wherein said alarm system is arranged to detect when current is breaking through the reference gas discharge tube and to initiate a degradation alarm, and wherein the alarm circuit loop is protected from overvoltage when current is breaking through the reference gas discharge tube.

2. The overvoltage protector circuit according to claim 1 , wherein the alarm circuit loop is arranged to be closed in its normal state when no current is breaking through the reference gas discharge tube.

3. The overvoltage protector circuit according to claim 1 , wherein the alarm circuit loop is arranged to be opened when current is breaking through the reference gas discharge tube.

4. The overvoltage protector circuit according to claim 3 , wherein a fuse means is arranged in the alarm circuit loop, which fuse means is arranged to be blown when current is breaking through the reference gas discharge tube and open the closed loop.

5. The overvoltage protector circuit according to claim 1 , wherein a link connection is arranged between the reference gas discharge tube and ground, said link connection comprises the fuse means and a diode means, wherein the fuse means is isolated from the communication line by the reference gas discharge tube and from the ground by the diode means.

6. The overvoltage protector circuit according to claim 5 , wherein the link connection comprises two links arranged in parallel, each link including a fuse and a diode, the fuses of the links composing said fuse means and the diodes of the links composing said diode means.

7. The overvoltage protector circuit according to claim 1 , wherein two or more supervised gas discharge tubes are connected to the same alarm circuit loop, over one or more reference gas discharge tubes.

8. A detector circuit for supervising degradation of an overvoltage protector including a gas discharge tube connected to a communication line for passing any harmful surge currents appearing in the line to ground, comprising a reference gas discharge tube arranged to be connected to the supervised gas discharge tube and to an alarm circuit loop connected to an alarm system, said reference gas discharge tube having a higher breakdown voltage than the supervised gas discharge tube, wherein said alarm system is arranged to detect when current is breaking through the reference gas discharge tube and to initiate a degradation alarm, and wherein the alarm circuit loop is protected from overvoltage when current is breaking through the reference gas discharge tube.

9. The detector circuit according to claim 8 , wherein a fuse means is connected between the reference gas discharge tube and the ground which fuse means is arranged to be blown when current is breaking through the reference discharge tube set the alarm circuit loop in a state of alarming a degradation.

10. The detector circuit according to claim 8 , wherein the alarm circuit loop is arranged to be closed and isolated from external signals and the ground in its normal state when no current is breaking through the reference gas discharge tube and that the loop is arranged to be opened when current is breaking through the reference discharge tube.