STI STI-3300 Wireless Doorbell Extender with Receiver
Overview
The STI-3300 is a wireless doorbell extender sensor designed to retrofit into an existing house doorbell box and transmit button presses to a wireless receiver up to 500 feet away (line of sight). This solves a real problem: when your primary doorbell location is too far from occupied spaces, or when you need audio notification in a secondary building, garage, warehouse office, or detached structure without running new wiring. The sensor operates directly off your existing doorbell's power supply — no separate power supply needed at the sensor. It pairs with the STI-3353 wireless chime receiver, which plugs into a standard 120 VAC outlet. This approach avoids costly rewiring and keeps installation simple enough for a security integrator to deploy in under an hour.
Key Features
- 500-foot wireless range (line of sight): Covers most residential properties and small commercial campuses without radio dead zones in typical outdoor or light-wall environments. Range reduces through walls and dense obstacles — plan for 100–200 feet in heavy construction.
- Retrofit into existing doorbell box: The STI-3300 sensor uses fork-shaped connectors that slide directly onto the doorbell's terminal screws (Front, Rear, Trans) without removing or cutting any existing wires. Disable power, mount the sensor with double-sided tape, slide connectors on, restore power — no electrician call-out.
- 433 MHz frequency, FCC and IC certified: Operates on the standard 433 MHz ISM band and is certified by both FCC and Industry Canada, eliminating regulatory risk in North American deployments. No licensing or frequency conflict with consumer WiFi or cordless phones.
- Automatic pairing: Front doorbell button pairs on first press after receiver is powered up. If a rear doorbell exists, it pairs automatically on subsequent use. No manual configuration codes or jumpers needed.
- Low and high volume settings on receiver: The STI-3353 receiver offers adjustable audio output so you can silence nuisance presses or ensure audible notification in noisy environments (warehouse floors, busy retail spaces).
- 120 VAC receiver power: The chime receiver plugs directly into a standard wall outlet — no batteries to replace, no PoE switch required. Ideal for offices, break rooms, or security desks where AC power is already available.
Installation and Wiring
Power down the existing doorbell circuit before opening the box. Mount the STI-3300 sensor inside or outside the doorbell housing using the provided double-sided tape — placement doesn't matter as long as the connectors reach the terminal screws. The sensor has three fork-shaped connectors labeled for the doorbell's Front (black), Rear (brown), and Trans (red) terminals. Slide each connector onto its corresponding screw without disconnecting the original wires. If your doorbell has no rear button, tape the brown connector and leave it disconnected. Restore power to the doorbell circuit, then plug the STI-3353 receiver into a 120 VAC outlet and press its pairing button. The front doorbell button will transmit immediately; any rear button will activate on first press.
Compatibility and Integration
The STI-3300 works exclusively with the STI-3353 wireless chime receiver — they are sold as a matched pair and cannot be separated. The sensor is compatible with any standard residential or light commercial doorbell that operates between 8 and 24 VAC, whether mechanical bell, buzzer, or electronic chime. This includes most aftermarket video doorbells that still maintain a hardwired connection. If you need to extend signal to multiple receivers or cover larger properties, you'll need to deploy additional STI-3300 / STI-3353 pairs on separate 433 MHz frequency channels or use a different product line.
What's in the Box
- 1x STI-3300 Wireless Doorbell Extender Sensor
- 1x STI-3353 Wireless Chime Receiver
- Double-sided mounting tape
Frequently Asked Questions
Q: What is the actual range of the STI-3300 in a typical installation?
A: Manufacturer spec is 500 feet line of sight. In outdoor or light-framed residential settings, expect 300–400 feet reliably. Through dense walls, metal studs, or long indoor corridors, range drops to 100–200 feet. Test your specific site before relying on coverage at the property edge.
Q: Can I use the STI-3300 with my existing video doorbell?
A: Yes, if your video doorbell still uses a hardwired connection to the existing transformer and doorbell circuit. The STI-3300 sensor connects to the same wires, so both the video doorbell and the extender can coexist. However, you cannot integrate the video doorbell's button with the wireless receiver — the sensor only captures mechanical or electronic doorbell presses on the circuit itself.
Q: Do I need an electrician to install the STI-3300?
A: No. You only need to turn off power to the doorbell circuit at the breaker, mount the sensor with tape, and slide the connectors onto the terminal screws. No wire cutting, splicing, or reconnection. Restore power and plug in the receiver. A security integrator can complete installation in 20–30 minutes.
Q: What happens if my house has both a front and rear doorbell?
A: The STI-3300 sensor has connectors for both. Slide the black connector onto Front, the brown onto Rear, and the red onto Trans (transformer/common). Both buttons will transmit to the same receiver. If you don't have a rear button, tape the brown connector and leave it disconnected.
Q: Is the STI-3300 outdoor-rated?
A: The sensor can be mounted inside or outside the doorbell box. No IP rating is specified, so avoid direct water spray or submersion. Most doorbell boxes are already semi-protected, and the sensor can mount inside for added protection if needed.
Q: What is the warranty on the STI-3300?
A: Manufacturer provides a one-year limited warranty covering defects in materials and workmanship. Contact the manufacturer or your supplier for warranty claim details.
The STI-3300 solves a logistics problem I see in warehouses and office parks where the main entrance is 200+ feet from the security desk or back office — hardwiring a new circuit is expensive and disruptive, but missing visitor alerts is a real security gap. What makes this design work is that it taps directly into your existing transformer voltage (no separate power supply at the sensor) and uses passive connectors, so there's no active circuit to troubleshoot. The 500-foot range spec and 433 MHz FCC certification mean you're not fighting WiFi interference or dealing with unlicensed frequency headaches. That said, the STI-3300 is a single-receiver design — if you need the same doorbell alert at the security desk, warehouse floor, and gate house, you'll need three separate STI-3300 / STI-3353 pairs.
Technical Highlights:
- 433 MHz ISM band, FCC and IC certified: No frequency licensing, no coordination with WiFi 2.4 GHz, and no risk of interference from cordless phones or nearby access points. Clean spectrum in North American deployments means reliable range without dead zones in typical environments.
- Automatic pairing on button press: No configuration codes, no jumpers to set, no pairing window to remember. First button press pairs the front doorbell; rear button pairs automatically on first use. Deploy and walk away — this is integrator-friendly.
- Fork-shaped connectors with no wire disconnection: This is the big time-saver. You slide connectors onto existing terminal screws; the original wires stay in place. Your video doorbell, mechanical bell, or electronic chime continues to function independently while the sensor captures the signal. No risk of cross-wiring or accidentally breaking the existing doorbell logic.
- 120 VAC receiver, no batteries: The STI-3353 receiver plugs into a wall outlet. No battery replacement schedule, no low-battery alerts, no chance of the chime going silent during a shift change because someone forgot to check the battery. Plug, pair, done.
Deployment Considerations:
- The 500-foot spec is line of sight — plan conservatively for indoor or multi-wall settings. If your security desk is behind metal studs or brick, test range before committing the receiver location. 200–250 feet is a safer assumption in dense environments.
- Single receiver per pair means you cannot multiplex one doorbell to several locations without buying additional STI-3300 / STI-3353 kits. If your warehouse needs desk, floor, and gate alerts from one button, budget for three units and three wall outlets.
Deploy the STI-3300 when your warehouse or office campus has a single vulnerable entrance (delivery dock, side gate, loading area) that is too far to hear a hardwired chime, and you want to avoid the cost and downtime of trenching new wiring or running new circuits. It's a retrofit play that works because it doesn't fight the existing infrastructure — it sits on top of it and broadcasts what's already happening.
