Random signature island circuit
US4868538A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Oct 7, 1988 |
| Grant date | Sep 19, 1989 |
| Priority date | — |
| Expiry date | Oct 7, 2008 |
Classification
- Technology area (CPC B)Performing Operations; Transporting
- CPC primaryB61L29/286
- WIPO fieldTransport
- WIPO sectorMechanical engineering
Abstract
An island circuit detects the presence of a train on a crossing island, and, in response, de-energizes a normally energized relay to activate a warning. A random signature signal is generated and transmitted through the rails from a transmitter to a receiver connected to the rails on either side of the island. If a train is present within the island, the wheels and axles form an electrical shunt, preventing the receiver from detecting the transmitted signal. The circuit employs solid state micro-electronic components and ancillary components, and embedded software for controlling and monitoring the circuit functions. The random signature signal is characterized by a relatively high voltage level but a low duty cycle on the order of ten percent, and has three variables: (1) frequency; (2) duration time of the pulse, or burst, of the signal; and (3) the delay between successive bursts. Each of the three variables randomly assumes any one of eight different discrete values. Each time a signal is received, the detector checks to determine whether the received signal matches the transmitted signature signal. If three consecutive transmitted and received signals do not match, the island …
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.