C7 Nurse Call, Intercom & Paging Systems — Questions and Answers
Question 1: Which UL standard governs the listing and testing requirements for hospital signaling and nurse call equipment?
- UL 294
- UL 681
- UL 1069 (Correct answer)
- UL 2572
Correct answer: UL 1069
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?
- 40 watts
- 80 watts (Correct answer)
- 100 watts
- 160 watts
Correct answer: 80 watts
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?
- Only at the patient station
- Only at the master station at the nurses' desk
- At the patient station or at the duty station outside the room (Correct answer)
- Only by a supervisor with a key switch
Correct answer: At the patient station or at the duty station outside the room
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?
- To power the intercom handset at the door
- To release an electric door strike or magnetic lock to grant entry (Correct answer)
- To activate the building's fire alarm
- To switch the intercom system to hands-free mode
Correct answer: To release an electric door strike or magnetic lock to grant entry
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?
- The 25V system allows longer runs with less signal loss
- The 25V system results in greater signal loss over distance and requires shorter runs or heavier wire (Correct answer)
- Voltage rating has no effect on cable run distance
- The 25V system is only used outdoors and distance is irrelevant
Correct answer: The 25V system results in greater signal loss over distance and requires shorter runs or heavier wire
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.
Question 6: Which wiring method is most appropriate for a concealed nurse call installation inside a hospital patient room where cables run through a plenum ceiling space?
- Standard CL2 rated cable (non-plenum)
- CMP (plenum-rated) cable per NEC Article 800 (Correct answer)
- Type NM cable in flexible conduit
- Any cable since nurse call voltages are below 50V
Correct answer: CMP (plenum-rated) cable per NEC Article 800
NEC Article 800 and Article 725 require plenum-rated cable (CMP or CL2P) when cables run through plenum ceiling spaces used for air return, regardless of the voltage level. Plenum-rated cables have low-smoke, flame-retardant jackets that prevent toxic smoke spread through HVAC systems.
C7 Nurse Call, Intercom & Paging Systems
Which UL standard governs the listing and testing requirements for hospital signaling and nurse call equipment?