Corrected entry: When Captain America and the Black Widow are in the Quin-jet on their way to rescue the hostages from the ship, Cap speaks into his wrist microphone to say "Secure Channel 7" to ensure that Black Widow's earpiece is working. She replies "Channel 7 secure", but you see that Captain America doesn't put his earpiece in his ear until after Black Widow replies. Cap has no way of knowing if his earpiece works at that point.
lionhead
19th May 2014
Correction: Actually the reason he says "secure channel 7" is just to ask Black Widow to secure channel 7 for them to make sure the hijackers can't hear them. She replies that channel 7 has been secured. Its got nothing to do with checking the earpieces.
lionhead