What did businesses in New York City start to do in the mid-1980's and what rationale did they use in Part I, Chapter 3?

According to Part I, Chapter 3, in New York City in the mid-1980's, businesses started to install buzzers to allow entry into stories with the permission of the attendant and use the rationale of protecting stores from crime. Williams thought this was a means of discrimination, especially after she was excluded from entering.