| 摘要 |
<p>An electronic control system particularly suited for use with an automatic fuel dispensing system uses a centrally located computer to supply serial polling signals to various sub-stations. At the sub-stations, the polling signals are decoded into signals used to control the operation of specific system relays operated by the system. The status of the decoded polling signals as well as the operating status of the relays is supplied back to the computer for verification. A time-out control circuit continuously monitors the input polling signals applied to the relay terminal. If activity does not appear on the input signal line at the terminal after a pre-established time interval, all of the system relays at the terminal are turned off or rendered inoperative, irrespective of the status of the relay control signal obtained from the output of the polling signal decoding circuit. As a consequence, if the remotely located computer should fail to properly operate for any reason, the system is placed in a "fail-safe" standby condition of operation.</p> |
