Note: This is not a duplicate of How do the Avengers Communicate? The question in the link is about Avengers:Age Of Ultron (2015) but this question is about The Avengers (2012)
In the Avengers (2012), in the climax fight how did the Avengers communicate with each other without any sort of ear equipment?
The inner ear piece communication technology seen in Avengers 2 was developed by SHIELD and introduced in Agents Of Shield S01E01 in 2013. Also Tony Stark created the little blue glowing earbud in Iron Man 3 (2013).
So how did the Avengers communicate without any ear equipment in the Battle of New York?
Iron Man can be neglected from the list because his suite has a built-in phone, but how did Captain America, Black Widow and Hawkeye communicate?