A common form of turning in a fire alarm is by using:

Using the telephone system to turn in a fire alarm is a common practice because it provides a reliable and immediate means of communication with emergency services. When a fire is detected, contacting the fire department via the telephone can ensure that an alert is sent out quickly, allowing for rapid response to the situation. Most fire departments are trained to receive emergency calls and understand the information they need to respond effectively, including the location of the fire and any hazards that may be present.

Additionally, telephones are widely accessible and can be found in various public and private settings, making them a practical choice for reporting fires. The use of a telephone system is also standard protocol in many fire safety plans, reinforcing its importance in emergency response scenarios. This effectiveness in communicating critical information during a fire incident underscores why this answer is appropriate.