| 摘要 |
<p>SIMPLIFIED CAB SIGNAL RECEIVER CIRCUIT This invention covers train cab signal equipment for receiving frequency modulated rail code signals which, when decoded, provide a zone speed control signal which the railway train traversing the track rail must obey in order to proceed at a safe speed. The invention includes a signal limiter circuit which prevents the signal supplied to the several code frequency responsive networks in the decoder unit from exceeding a predetermined maximum value in order to assure a welldefined frequency bandwidth to which respective code filters in the frequency responsive networks are sensitive, so that only a single network is responsive to any given code signal. In addition, the limiter circuit supplies the respective frequency responsive networks with a code signal whose amplitude is proportional to rail current so long as the code signal is below the maximum level set by the limiter. This permits a level detector associated with each code filter to monitor the code signal received for minimum level detection in order to assure that the rail current code signal is a valid code signal.</p> |
