The samphold~ object samples the left inlet audio signal whenever the control signal on right inlet is decreasing.
A toggle switch, operating at 10 ms, forces sampling whenever it is undergoing 1->0 transition, and the sampled audio will go to the left channel.
The audio signal is a sinusoidal at 5-Hz, too low to be heard by humans. The audio objects throw~ and catch~ are used so are our connections are cleaner. The thrown audio forms the right channel.
The audio waveform shows the effect of the samphold~: