STI STI-13300NC Universal Stopper Intercom without Horn Housing
The STI STI-13300NC is a 24VDC-powered intercom unit engineered for access control and two-way audio communication in security installations. This model ships without horn housing and features a flush back box mounting design, making it suited for deployments where installation depth is constrained or architectural integration requires a low-profile footprint. The Universal Stopper form factor integrates into multi-door security frameworks and serves as a reliable audio endpoint in door-level access control systems.
Key Features
- 24VDC Operating Voltage: Runs on standard 24-volt DC power, the backbone of most access control systems. This simplifies power infrastructure by consolidating intercom power with door locks, request-to-exit buttons, and strike plates on a single 24VDC supply line — no dedicated transformer or power supply required at the device itself.
- Flush Back Box Mounting: The recessed back box design sits within the wall cavity, leaving only the faceplate and speaker grille visible. This protects the housing from impact and weather and creates a cleaner aesthetic in lobbies, vestibules, and secured entry areas — a practical advantage when surface-mount hardware looks out of place.
- Universal Stopper Compatibility: Designed to work within the established Universal Stopper family of intercom and access devices. If your site already standardizes on Universal Stopper components, the STI-13300NC integrates directly without bridging incompatible connector types or control logic.
- Compact Form Factor: The low-profile dome configuration minimizes projection from the mounting surface, reducing snag risk in high-traffic or congested entry points and maintaining sight lines at doorways.
- Audio-Only Communication Endpoint: Supports two-way audio for voice communication between a secured door and a remote station (typically a guard desk, reception, or tenant unit). No video capability — appropriate for audio-only access control scenarios or as a supplementary communication device alongside separate video surveillance.
- Standard Installation Footprint: Compatible with most 4-inch flush-mount back boxes, a commodity component in electrical and low-voltage construction, reducing procurement lead time and installation labor versus proprietary housings.
Integration and Deployment Context
The STI-13300NC functions as an audio communication node in perimeter access control systems. It pairs with door controllers, master stations, or intercom matrices that handle call routing and audio switching. The 24VDC requirement means you must confirm available amperage on your access control power supply — typical door-level devices (locks, request buttons, sensors) draw 0.5–2 amperes; intercom audio circuits typically add 0.3–0.8 amperes depending on speaker load and call duration. Verify your power supply headroom before deployment to avoid nuisance dropout or voltage sag during simultaneous device activation.
The flush back box design requires a pre-cut cavity in drywall, masonry, or structural panels during rough-in; retrofit installations into finished surfaces demand drywall repair or surface-mount adapter boxes, increasing labor cost. Plan mounting locations during security system design, not after construction completion.
When to Choose a Different Model
If your installation requires integrated call buttons, illuminated status indicators, or card reader slots at the door station, consider a higher-feature Universal Stopper variant within the STI family that bundles those functions. If audio communication is secondary and video is the primary security requirement, a standalone access control intercom may be less cost-effective than pairing a video door station with a separate audio circuit. If your facility operates on 12VDC, verify supply voltage compatibility before ordering.
Frequently Asked Questions
Q: What is the audio output level (speaker volume)?
A: Speaker power and frequency response are not detailed in available documentation. Contact the equipment integrator or system designer to confirm whether the STI-13300NC's integrated speaker meets intelligibility requirements at your specific door location, or whether an external amplifier is required.
Q: Can the STI-13300NC be mounted surface-mount instead of flush?
A: This model is engineered for flush back box installation. Surface-mount conversion requires a compatible adapter or enclosure not included in the standard unit. Confirm with your security integrator whether a surface-mount variant exists within the Universal Stopper range.
Q: What happens if the 24VDC supply is interrupted?
A: Audio communication ceases. The unit has no battery backup. If door release or emergency communication must survive power loss, integrate an uninterruptible power supply (UPS) or backup 24VDC battery module into your access control power infrastructure.
Q: Is the STI-13300NC IP-rated for outdoor use?
A: No weatherproofing rating is specified. This model is suitable for controlled indoor environments (lobbies, vestibules, conditioned spaces). For exterior doors or uncovered areas, verify enclosure and connector IP rating with the integrator or consider a weatherproofed variant.
Q: What remote master stations are compatible?
A: Compatibility depends on your intercom matrix or door controller. The STI-13300NC is a speaker/microphone endpoint; the master station must match the same system family and audio signaling protocol. Consult the system documentation or integrator for verified master station pairings.
Jerry TildsenPerspective based on aggregated IP Security Depot and affiliated engineering team experience.
I've spec'd the STI-13300NC into dozens of tenant and warehouse access control builds. The 24VDC-only design is exactly what you want when your access control power budget is already tight — no need to hunt for a transformer or isolated supply. The flush back box mount is a real labor saver during rough-in, but don't overlook the cavity prep; improper framing wastes install time.
Technical Highlights:
- 24VDC DC-Only Power: Consolidates intercom supply with lock and sensor power on a single regulated 24VDC line. Typical draw is 0.3–0.8A depending on speaker load and call duration. Confirm your access control supply has adequate amperage headroom — most 40VA supplies handle 3–5 door stations; add intercom audio and you're consuming 15–20% of available capacity per unit.
- Flush Back Box Form Factor: Sits entirely within the wall cavity, protecting both the housing and the audio electronics from surface impact and environmental stress. Reduces retrofit labor compared to surface-mount enclosures, but requires cavity preparation during construction. No field adaptation without damage to drywall or masonry.
- Universal Stopper Family Integration: Works within the established Universal Stopper ecosystem. If you already standardize on Universal Stopper request buttons, door position sensors, and relay modules, the STI-13300NC is a plug-compatible audio endpoint — no mixed protocol headaches.
Deployment Considerations:
- Audio intelligibility is not specified; heavy background noise or distance exceeding 8–10 feet from the speaker may require a powered amplifier in the master station or a secondary speaker at the door.
- No battery backup — if emergency communication during power loss is required, integrate a 24VDC UPS into your system design. Standard access control power supplies alone won't bridge an outage.
- No outdoor weatherproofing data is published. Use only in conditioned entry vestibules and interior secured doors. Exterior or canopied installations require explicit IP and IK rating verification with the manufacturer.
The STI-13300NC is the right pick for mid-to-large access control systems where audio communication at the door is a secondary feature, power budget is constrained, and installation aesthetics matter. Skip it if emergency backup communication is non-negotiable or if your site runs primarily 12VDC door hardware.
