33 CFR § 157.12a - Definitions.
As used in §§ 157.12a through 157.12g—
Control section means a unit in a monitoring system composed of the items specified in § 157.12d(a)(4)(viii).
Control unit means a device that receives automatic signals of oil content of the effluent ppm, flow rate of discharge m 3/hour, ship's speed in knots, ship's position-latitude and longitude, date and time (GMT, Greenwich Mean Time), and status of the overboard discharge control. The control unit makes automatic recordings of data as specified in § 157.12d(h)(2).
Oil discharge monitoring and control system or monitoring system means a system that monitors the discharge into the sea of oily ballast or other oil-contaminated water from the cargo tank areas and comprises the items specified in § 157.12d(a)(4).
Overboard discharge control means a device that automatically initiates the sequence to stop the overboard discharge of the effluent in alarm conditions and prevents the discharge throughout the period the alarm condition prevails. The device may be arranged to close the overboard valves or to stop the relevant pumps, as appropriate.
PPM means parts of oil per million parts of water by volume.
Starting interlock means a facility that prevents the initiation of the opening of the discharge valve or the operation of other equivalent arrangements before the monitoring system is fully operational when use of the monitoring system is required by the Convention.