51.   Using radio signals, it directly measures the electrical activity of the heart.

52.   Using signals devised by Goodman, Smith answered questions with eye blinks to check his mental functions.

53.   Using electronic signals, the computer chip identifies which programs to block based on their program ratings.

54.   Using hand signals, he asked the photographers to turn off their lights.

55.   Using radio signals, Fast Lane tracks when and where cars enter and leave the roadway or pass collection points.

56.   We use hand signals with the two analysts.

57.   What few casual GPS users realize, however, is that these same satellite signals can be used for more than just determining time and location.

58.   With special GPS receivers, U.S. forces can use the signals to calculate precisely where they are or where they want to go.

59.   After boarding the vessel, the officers headed for the bridge and began issuing commands using hand signals, the newspaper said.

60.   Established procedures call for Peruvian fighters that approach suspect planes to use hand signals and send radio messages to make contact.