The two functions, SP and SLP, refer to the standard play and extended play recording modes. The SP button stands for standard play, and allows the television programs to be recorded at a slower rate, thereby increasing playback quality. Extended play records longer videos, but decreases playback quality.
The SP, or standard play, function allows for up to 2 hours of recording capability. Extended play allows a continuous recording for more than 4 hours; however, it does decrease the overall picture and audio quality of the program it is recording. SLP videos have been known to fail over time due to the speed at which they were recorded.