What are the different types of PSAPs? (Public safety answering point)

PSAP Definition:

Public safety answering points (PSAP), also known as public safety access points are dedicated 24/7 call centers responsible for answering 9-1-1 emergency calls, dispatching the appropriate emergency services, and transferring calls to other specialized agencies. According to specific operational policies, PSAPs can dispatch units on the field such as police officers, firefighters, and ambulance/paramedic services. PSAPs vary in terms of the population they serve and can be found both in large cities or smaller towns.