C7 Nurse Call, Intercom & Paging Systems

Question 1

Which UL standard governs the listing and testing requirements for hospital signaling and nurse call equipment?

Accepted Answer

UL 1069

Answer

UL 1069 is the Standard for Hospital Signaling and Nurse Call Equipment. It covers the electrical and mechanical requirements for patient stations, duty stations, and master stations in nurse call systems. UL 294 is for access control, UL 681 is for burglar alarm installation, and UL 2572 is for mass notification.

Question 2

In a zone paging system serving a multi-story office building, the paging amplifier output must be matched to the speaker load. If the amplifier is rated at 70.7 volts and the total speaker tap wattage on a zone is 80 watts, what minimum amplifier wattage is required for that zone?

Accepted Answer

80 watts

Answer

The amplifier must be rated at least equal to the total speaker tap wattage on the zone — in this case 80 watts. It is best practice to derate to 80% of amplifier capacity in design, meaning an 80W zone would call for a 100W amplifier in real practice, but the minimum required rating equals the total tap load.

Question 3

A nurse call patient station in a hospital room should be wired so that a call can be canceled from which location?

Accepted Answer

At the patient station or at the duty station outside the room

Answer

Nurse call systems are designed so that a call can be answered and canceled at the duty station (corridor dome light/annunciator outside the room) or at the master station. This allows staff to acknowledge a call at the point of response without requiring the patient to cancel it, improving workflow and accountability.

Question 4

When installing a two-wire intercom system in a residential building, what is the primary function of the door strike output on the master intercom station?

Accepted Answer

To release an electric door strike or magnetic lock to grant entry

Answer

The door strike output on an intercom master station sends a momentary voltage signal to an electric door strike or mag-lock, releasing the door latch to grant entry. This is the core access-granting function of a door intercom entry system.

Question 5

In a paging system using a 25-volt distribution line rather than a 70.7-volt line, what is the practical effect on the maximum cable run distance for a given speaker tap load?

Accepted Answer

The 25V system results in greater signal loss over distance and requires shorter runs or heavier wire

Answer

At the same wattage, a 25V distribution system carries higher current than a 70.7V system (P=V²/R relationship). Higher current causes greater resistive voltage drop in the cable, limiting practical run lengths or requiring larger gauge wire to compensate. The 70.7V (and 100V) constant-voltage systems were developed specifically to allow long runs with small wire.

(C7) California C7 Low Voltage Systems Contractor Certification Practice Test

(C7) California C7 Low Voltage Systems Contractor Certification Practice Test

C7 Nurse Call, Intercom & Paging Systems