The Station Pump Controller can operate in two modes: Automatic or Manual.
In the automatic mode, the SPC maintains a dialogue with the fuel pumps, checking their condition and authorizing each transaction automatically, storing the information of each transaction in an internal buffer (protected against power failures), which can be downloaded from the PC. In this mode the Station Pump Controller is completely autonomous and enables the operation of the fuel pumps even if the computer system is not available. Thus there is not need to change the mode of operation of the fuel pumps
from “two-wire” to “stand-alone” in the event of faults in the computer, because the SPC continues authorizing and recording each transaction, and they will be recovered when the system in the PC is reestablished.
Running in manual mode, the PC is in charge to control the fuel pumps situation and must authorize each transaction when the fuel pumps requires it. Also, when the transaction ends, the SPC tells the PC that there is a transaction for reading and the PC must read it before authorizing the fuel pump again.
The advantage of the manual mode is that the PC is taking the complete control of the fuel pumps, and then “allow / disallow” fuel pumps to make each transaction: (pre-payment, post-payment and self-service). In the event that the Station Pump Controller is operating in this mode, and a failure in the PC happens, the system has incorporated a command to switch to automatic mode and continue with the fuel dispatch. The SPC will continue into autonomus mode until the system on the PC has been restored.