What is the primary purpose of the pressure indicating transmitters in the Type 3 system?

The primary purpose of pressure indicating transmitters in the Type 3 system is to monitor the pressure in the system and provide signals based on that pressure. When the pressure drops below a predetermined level due to system demand, the transmitter sends a signal to "call on the lead pump." This allows for the lead pump to engage and maintain system pressure, ensuring that the desired flow and operational requirements are met.

This process is crucial for maintaining system efficiency and reliability. By effectively managing the lead pump operation, pressure indicating transmitters help prevent issues such as cavitation or inadequate flow, which could result in operational failures or equipment damage. The correct choice reflects the essential function of these transmitters in automating the operation of the water and fuel systems, ensuring that the lead pump is activated when needed.