NOTE: After this article was printed, Analog Devices changed the LTspice model for the ADG1209 analog switch IC. Where the original version contained a single switch, the updated version of the switch now has two switches to match the actual part as it's sold. Whether or not you'll have a problem running the circuit depends on how recently you updated LTspice. If you load the S&H Circuit.asc file and both analog switches and their Address Selection Table comments are in disarray, load the other .asc file marked NEW and that will work correctly.