Samantha Goes South for a Spell - S5-E2
Other mistake: Serena tells Darrin that Samantha won't know him back in the 19th century New Orleans because she hadn't been born yet. In Aunt Clara's Victoria Victory, we know Samantha was alive in the 19th century because she and Endora were "in Tibet at the time."
Samantha Goes South for a Spell - S5-E2
Other mistake: Darrin doesn't recognise Serena posing as Samantha. We know from "That Was No Chick, That Was My Wife" that he can tell the difference. This happens in several episodes.
Answer: Telstar was an early communications satellite system. Darrin, in a particularly sexist manner reflective of this era, is saying that telling a secret to a woman means it is guaranteed to be "broadcasted" to multiple people.
raywest ★