Within five years of the first radio in 1933, two-way radio was introduced into the cars of the Bayonne, New Jersey police. The two-way radio was quickly adopted throughout the country.
As communication was now possible between the police station and the cars, the police box quickly vanished. However, the old police box phones can still be seen in San Fransisco. In 1940 FM radio communication was introduced in Hartford, CT. The quality of the communication system was improved by using FM instead of AM.