Claims
- 1. An arrangement for protecting telecommunications equipment from a voltage transient, which comprises
- (1) a voltage clamping device having a capacitance and connected between a current-carrying line of a circuit comprising the telecommunications equipment and ground,
- (2) a capacitor having a capacitance value up to 1 .mu.F connected in series with the voltage clamping device,
- (3)an inductance having a value of from 1 .mu.H to 100 mH a series connected in the line, and
- (4) a high-energy foldback device connected between the current-carrying line and ground,
- under normal operating conditions the arrangement acting as an LC filter whose high frequency break-point
- (a) is determined by (i) the capacitance of the voltage clamping device; (ii) any additional capacitor optionally connected in parallel with the voltage clamping device and the inductance, and (iii) is in the range of from 1 kHz to 10 MHz, and
- (b) falls when the arrangement is subjected to a voltage transient sufficient to cause the voltage clamping device to conduct, to a value that is determined by the values of the capacitor and the inductance.
- 2. An arrangement as claimed in claim 1, wherein the inductance has a value of up to 1 mH.
- 3. An arrangement as claimed in claim 1, which has a total series resistance in the range of from 1 to 50 ohms.
- 4. An arrangement as claimed in claim 4, which has a total series resistance in the range of from 3 to 10 ohms.
- 5. An arrangement as claimed in claim 1, wherein the high frequency break point, when the arrangement is subjected to a voltage transient sufficient to cause the voltage clamping device to conduct, occurs at a frequency not higher than 0.1 times the frequency of the break-point under normal operation.
- 6. An arrangement as claimed in claim 5, wherein the high energy foldback device is a gas discharge tube or a voltage controlled triac.
- 7. An arrangement as claimed in claim 1, which includes an overcurrent protection device series connected in the current-carrying line.
- 8. An arrangement as claimed in claim 7 wherein the overcurrent protection device is a PTC device.
- 9. An arrangement as claimed in claim 1, which includes an additional voltage clamping or foldback device connected across the capacitor, which capacitor is connected in series with the voltage clamping device and has a capacitance value up to 1 .mu.F.
- 10. A circuit protection unit which comprises two arrangements for protecting telecommunications equipment, each of which arrangements is series connected in a respective current-carrying line of a pair of current-carrying lines and each of which arrangements is connected to a common ground to form a circuit, each of the arrangements comprising
- (1) a voltage clamping device having a capacitance and connected between a current-carrying line of the circuit and ground,
- (2) a capacitor having a capacitance value up to 1 .mu.F connected in series with the voltage clamping device,
- (3) an inductance having a value of from 1 .mu.H to 100 mH series connected in the line, and
- (4) a high-energy foldback device connected between the current-carrying line and ground,
- under normal operating conditions each arrangement acting as an LC filter whose high frequency break-point
- (a) is determined by (i) the capacitance of the voltage clamping device, (ii) any additional capacitor optionally connected in parallel with the voltage clamping device and the inductances, and (iii) is in the range of from 1 kHz to 10 MHz,
- falls when the arrangement is subjected to a voltage transient sufficient to cause the voltage clamping device to conduct, to a value that is determined by the values of the capacitor and the inductance.
Priority Claims (1)
Number |
Date |
Country |
Kind |
90 21 222.6 |
Sep 1990 |
GBX |
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CROSS-REFERENCE TO RELATED APPLICATIONS
This application is a continuation of commonly assigned application Ser. No. 08/030,307, filed May 13, 1993, now abandoned.
US Referenced Citations (11)
Foreign Referenced Citations (1)
Number |
Date |
Country |
590491 |
Nov 1989 |
AUX |
Continuations (1)
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Number |
Date |
Country |
Parent |
30307 |
May 1993 |
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