A soldier patrolling the Great Wall witness an attack from the Hun army. In this example of smoke signals, one of the oldest forms of long-distance communication, he lights one of the beacon towers to warn the rest of China about an enemy invasion.
In this episode an Aerial Anomaly is reported over at least seven locations in Los Angeles. These observations let Charlie plot the aircraft's likely flight path by using a new way of removing noise from noisy signals ("Squish-Squash").
George discovers that when he wears a wedding band, women come on to him. The band signals 1) that you are not gay, and 2) that you are of marriageable quality. A girl discusses the signal with George; she uses the ring as a screening device.
A girl calls Jerry and tells him she needs to be in town for a conference but can't find a decent hotel room in Manhattan. George and Kramer say that these are signals. The girl arrives, and sends many additional signals (at least Jerry thinks she does), but ultimately tells Jerry that she's engaged. What Jerry needs is a screening device.
Jerry gives Elaine cash for her birthday, thinking she can spend it on whatever she likes best. But Elaine is mortified; she wanted a thoughtful gift that signaled Jerry had put great thought into his gift. Kramer enters and does just that—gives Elaine a thoughtful gift.