Did they have radios yet? Or did they simply receive orders in person while at "headquarters", and then have to carry them out without the ability to radio for backup?
The first police force to use radio communications was the Connecticut State Highway Patrol, in 1940. During the 1930s, most big cities in the United States and Great Britain had a system of call boxes through out their jurisdiction. This web site shows Baltimore Maryland got their first call boxes in 1885 and the last ones were removed in 1989 and 1990. The police patrolmen carried a key to open the box and could send eleven different signals to their precinct office. Police call boxes were similar to fire alarm boxes, but could send a larger number of messages back to the police station.
http://baltimorecitypolicehistory.com/citypolice/city-police-insight/police-call-box.html