From the photo series "A Time to Speak" by Morris Engel:

In the 1970's, Engel did a series of photographs called, "A Time to Speak" which is about people engaged in private conversations in public places. Engel saw a drama in the situations he encountered all over New York City. These phone booths once a mainstay of New York, are now obsolete and have vanished. The booths enabled people to be so wrapped up in their own situation or conversation , so that they would be unaware of any camera.

Via PuNk-and-StuFF.