US 2004/0057181 A1 · Polling loop short and overload isolator (VSOI)

Abstract

A Vplex polling loop device is disclosed which can automatically detect and isolate shorted or overloaded sections of a polling loop, before or after polling loop power and signaling is switched to the output of the device, permitting normal operation of the remaining portion of the polling loop. The Vplex short and overload isolator (VSOI) is usable on former, existing, and future polling loop systems without the need for any software or hardware changes to the associated controls, and may also be used on 2-wire DC voltage distribution systems within the voltage and current limits of the VSOI. It is capable of multiple use anywhere on a polling loop while requiring minimum power from the polling loop. Finally, in the process of detecting and isolating a short or overload on its output, it prevents that short or overload from causing other VSOI devices on the loop to erroneously disconnect their protective branches of the loop.

Claims24

Dependent claims

A Short and Overload Isolator (SOI) device, having an input and an output, for detecting and isolating shorted or overloaded sections of a 2 wire polling loop, comprising:

a. a bidirectional switch connecting the SOI input to the SOI output, wherein as polling loop power is initially applied to the SOI input, the switch is maintained OFF for a time while the SOI output is electronically tested for a possible complete or resistive short, and if a short is detected, the switch is maintained OFF, establishing a disconnected polling loop branch until the short is removed;
b. a uni-directional drive circuit which, if a short is not detected, is applied to the SOI output to test for possible overloads or device powered-on shorts, wherein the uni-directional drive circuit avoids possible powered-on shorts on the SOI output from temporarily appearing on the SOI input, and if an overload or powered-on short is detected, operation of the drive circuit is terminated and the switch is maintained OFF, establishing a disconnected polling loop branch until the short is removed, and if an overload or powered-on short is not detected, the switch is turned ON, establishing bi-directional connection from the SOI input to the SOI output and normal polling loop signaling operation.

A method of detecting and isolating shorted or overloaded sections of a polling loop by a Short and Overload Isolator (SOI) device having an input and an output which is associated with a branch of the polling loop, which SOI performs the following steps:

a. as polling loop power is initially applied to the SOI input, a switch connecting the SOI input to the SOI output is maintained OFF for a time while the SOI output is electronically tested for a possible complete or resistive short, and if a short is detected, the switch is maintained OFF, establishing a disconnected polling loop branch until the short is removed;
b. if a short is not detected, a current limited uni-directional drive circuit is applied to the SOI output to test for possible overload or device powered-on shorts, wherein the unidirectional circuit avoids possible powered-on shorts on the SOI output from temporarily appearing on the SOI input, and if an overload or powered-on short is detected, operation of the drive circuit is terminated and the switch is maintained OFF, establishing a disconnected polling loop branch until the short is removed, and then returning to step a;
and
c. if an overload or powered-on short is not detected, the switch is turned ON, establishing bidirectional connection from the SOI input to the SOI output and normal polling loop signaling operation.

1 more element

Dependencies are inferred from the claim text.

Polling loop short and overload isolator (VSOI)

Life of this patent

Polling loop short and overload isolator (VSOI)

Life of this patent

Abstract

Claims24