An office has an automated lighting system. When movement is detected in the office the lights are switched on. If movement is not detected for a period of 2 minutes the lights are switched off. The system uses a sensor and a microprocessor.

Mark scheme

Marking points from the official mark scheme (May/June 2019). The mark or mark type is shown in brackets.

1. [6] Six from: Motion sensor is used Sensor sends data/signal to microprocessor Data/Signal is converted from analogue data to digital data (using ADC) Value to compared to stored value(s) // If value is outside range/matches ... ... microprocessor sends signal to switch lights on ... actuator used to switch light on/off ... timer is set for 2 minutes Every time movement is detected the timer is reset When timer reaches 0/120/times out microprocessor sends signal to switch lights off Process is continuous
2. [3] Three from: Read only memory Non-volatile memory // Contents of memory are retained when power is turned off//permanent storage Primary storage // directly accessed by the CPU Holds firmware/boot-up instructions/start-up instructions/BIOS Cannot be written to