Scaling a video intercom system from a single screen to a multi-room setup transforms a simple appliance installation into a low-voltage engineering project. The ANJIELO SMART 94206B-AHDBK7 is frequently sold in a 1-Doorbell + 4-Monitor configuration, intended for larger villas or multi-level apartments. However, simply plugging in four screens without understanding the underlying signaling topology is a recipe for system instability.
This article examines the electrical and physical constraints of expanding the ANJIELO system, specifically focusing on impedance management, power distribution, and access control integration.
The Wiring Topology: Parallel vs. Series
In a multi-monitor configuration, the “Call” signal and the video feed must be distributed to all stations simultaneously. The ANJIELO system typically utilizes a 4-wire bus architecture. The four cores carry:
1. Audio
2. Ground (GND)
3. Video (AHD/CVBS)
4. Power (VCC)
For the 1+4 setup, the wiring is rarely a simple “star” configuration where all wires meet at the doorbell. instead, it often involves a daisy-chain (series-parallel) sequence or a central distribution block. The critical engineering challenge here is impedance matching.
Video signals are sensitive to reflections caused by improper splicing. If a user simply twists five video wires together (one from the doorbell, four to monitors) without a proper distribution block or impedance matching, the video signal will suffer from “ghosting” (double images) due to signal reflection. Installers must strictly follow the manufacturer’s pin-out diagram, ensuring that the “In” and “Out” ports on the monitors are used correctly if the system supports daisy-chaining, or use a dedicated video splitter if a star topology is required.
Power Budget and Voltage Drop
A common failure in multi-monitor installations is voltage drop. The standard kit operates on DC 12V. Each indoor monitor typically requires its own power source (AC 100-240V to DC 12V 2A adapter).
Critical Constraint: Do not attempt to power all four monitors and the outdoor unit from a single 2A adapter. The inrush current when all four monitors wake up simultaneously (screen backlight on + chime activated) can exceed the amperage rating of a single supply, causing a system reboot loop.
Furthermore, the wire gauge supplying the outdoor unit matters. The outdoor unit draws power from the primary indoor monitor via the 4-wire cable.
* Scenario: A 50-meter run using standard CAT5e cable (which uses thin 24AWG wires).
* The Physics: 24AWG wire has a resistance of approx. 0.084 ohms per meter. Over a 50m loop (100m total wire path), resistance is significant. If the outdoor unit pulls 500mA (especially when IR LEDs are on), the voltage at the doorbell could drop below the 10.5V operational threshold.
* Solution: For runs over 30 meters, users must upgrade to RVV4 0.75mm² or 1.0mm² cable to minimize resistance and ensure the camera receives full voltage.
Integrating Electronic Locks: The NO/NC Logic
One of the most powerful features of the 94206B system is its ability to drive electronic locks, transforming it into a full Access Control System. However, the “Unlock” button on the monitor is just a trigger; the wiring depends on the lock type.
The system generally provides a dry contact relay or a 12V pulse. Installers must distinguish between two lock states:
1. Fail-Secure (Normally Open – NO): Electric strikes that require power to unlock. If power fails, the door remains locked.
2. Fail-Safe (Normally Closed – NC): Magnetic locks (Maglocks) that require continuous power to stay locked. If power is cut, the door opens.
The Flyback Diode Necessity
When controlling a magnetic lock or a solenoid strike, the inductive load creates a voltage spike (flyback) when the power is cut. This spike can flow back into the intercom and damage the delicate circuitry of the outdoor unit.
* Engineering Mandate: Always install a flyback diode (e.g., 1N4007) across the lock terminals (Cathode to Positive, Anode to Negative). This shunts the spike and protects the ANJIELO doorbell unit from premature failure.
Environmental Hardening and Mounting
The outdoor unit is rated for -40~50, covering most inhabited climates. However, the IP (Ingress Protection) rating relies heavily on the installation quality. The unit comes with a rain cover, but water can still wick down the cable and into the rear port.
Installation Standard: always create a “Drip Loop”—a U-shaped bend in the cable just before it enters the camera unit. This gravity-based trap forces water to drip off the bottom of the loop rather than running down the wire directly into the connector. Failure to include a drip loop is the #1 cause of water damage in wired intercoms, regardless of the manufacturer’s weatherproofing claims.
Summary
Expanding the ANJIELO SMART system to a 4-monitor setup offers comprehensive coverage for large properties, but it demands respect for electrical principles. By ensuring adequate wire gauge (RVV4), distributing power loads correctly across multiple adapters, and protecting the circuit with flyback diodes when adding locks, users can build a commercial-grade access system at a consumer price point.
