Comelit 1224A Simplebus Additional Entry Unit
The Comelit 1224A is an additional entry unit designed for Simplebus intercom systems, enabling multi-point access control in residential complexes, apartment buildings, and small commercial properties. This compact module expands your existing Simplebus infrastructure without requiring central system reconfiguration. The 1224A mounts discreetly at secondary entrances, service doors, or auxiliary access points, allowing visitors and delivery personnel to request entry from any networked door station while maintaining centralized call routing and resident control.
Key Features
- Simplebus Protocol Compatibility: Operates natively on Comelit Simplebus topology — no bridge equipment or protocol translation required. Plug-and-play integration with existing door stations, handsets, and video intercoms.
- Compact Wall-Mount Form Factor: 2.36" W × 3.35" H × 1.38" D footprint — designed for architectural discretion at secondary entrances, loading docks, or service areas without visual obtrusiveness.
- Bus-Powered Operation: Draws power from Simplebus twisted-pair cabling — no separate 12V/24V supply line required at the unit location, reducing installation labor and conduit complexity.
- Visitor Call Routing: Incoming calls from the 1224A ring at designated handsets or video intercoms within the system. Call distribution logic remains centralized, simplifying multi-unit policy management.
- Professional-Grade Construction: Stainless steel or anodized aluminum faceplate options (per configuration) resist corrosion in high-traffic entry vestibules and exterior-mounted applications.
- Audio Codec Transparency: Maintains full wideband or narrowband audio paths depending on your Simplebus handset configuration — no audio degradation on secondary access points.
The 1224A is the standard accessory for scaling Simplebus deployments beyond the primary entrance. In apartment buildings, this translates to a single control philosophy across all entry points — residents manage access from their existing handset or video intercom, and system administration remains centralized. Unlike bolt-on intercom expansion cards that demand NVR or dedicated power distribution, the 1224A leverages existing bus infrastructure, keeping capex and installation time linear rather than exponential as building size grows.
Comelit Simplebus architecture was designed for resilience in multi-unit environments. The 1224A inherits that philosophy — it does not introduce single points of failure. If a secondary entry unit experiences a hardware fault, calls can be manually rerouted to the primary entrance or an adjacent handset without bringing down resident-to-visitor communication at other doors. This is particularly valuable in occupied residential properties where access interruption triggers tenant complaints and emergency call-out costs.
Installation footprint is minimal. A single twisted-pair run from your Simplebus controller (or from an intermediate wall-mounted unit) provides both signal and power. The 1224A mounts flush or semi-recessed in a standard electrical box; no conduit re-routing or HVAC coordination is needed. On retrofit projects where aesthetic impact drives decision-making, the compact depth and low profile reduce the framing work that would be required for larger intercom modules.
The 1224A is fully compatible with Comelit Simplebus handsets, video door stations, and call management software. Cross-building or multi-property Simplebus networks can incorporate multiple 1224A units at each location without address conflicts or call-routing ambiguity — the bus protocol handles automatic unit discovery and numbering. This modularity makes the 1224A suitable for property management firms operating chains of small residential properties, where standardized access hardware simplifies training and spare parts logistics.
Marty AllisonPerspective based on aggregated IP Security Depot and affiliated engineering team experience.
The Comelit 1224A is a workhorse expansion module we've deployed consistently across mid-rise residential retrofits and small commercial complexes. What makes it stand out is simplicity — it doesn't introduce new power infrastructure, doesn't demand firmware updates, and doesn't require property managers to learn a second control interface. We've seen integrators hesitate on Simplebus because they worry about scaling beyond a single entrance. The 1224A removes that objection entirely. In a 40-unit apartment building, you install one at the main lobby, one at the rear service entrance, and (if building policy requires it) one at the ground-level loading dock. All three units report to the same residential handsets or video intercom. A resident in Unit 3B presses one button to see who's at any of the three doors. That operational simplicity translates to fewer resident support calls and lower annual maintenance burden. Against wireless or cellular intercom retrofits, the 1224A wins on cost-per-installation and eliminates battery replacement cycles. Against larger IP intercom expansion cards, it wins on physical footprint and integration overhead. The main trade-off is that you're locked into Simplebus topology — there's no SIP mode, no cloud failover, and no mobile app integration (Comelit does offer mobile apps, but they're Comelit-ecosystem only). For properties that value standardization and low-touch operations, that's not a limitation; it's a feature. For properties that demand open-standards interop and cloud backup, the 1224A isn't the right fit.
Technical Highlights:
- Simplebus Bus Architecture: The 1224A operates on Comelit's proprietary twisted-pair bus — no PoE switches, no DHCP, no subnet planning. Single cable carries both power and signal. In retrofit scenarios where network infrastructure is absent or inaccessible, this eliminates a major capex hurdle and shortens installation cycles by 2–3 days per site.
- Call Routing Logic: Incoming calls from the 1224A trigger simultaneous or sequential ring at designated handsets, handset groups, or video stations. The calling unit (2.36" × 3.35") reports its location via bus-level metadata so display labels auto-populate on video systems. No manual call-plan configuration required beyond initial system setup.
- Audio Path Fidelity: Full wideband audio passthrough on Simplebus lines carrying Comelit handsets with wideband codecs. If your system uses narrowband handsets (older stock), audio quality degrades gracefully to narrowband on the 1224A — no codec negotiation hiccups.
- Compact Mounting Depth (1.38"): Fits in standard US electrical boxes (2-gang or single-gang with trim ring) without protruding beyond finished wall surface. This matters in high-traffic lobbies and vestibules where protruding hardware creates trip hazards and damage liability.
- No Firmware or Network Overhead: Unlike IP intercom modules that require periodic security patches and network monitoring, the 1224A has no software attack surface and no remote management interface — it's purely a passive bus node. Total cost of ownership reflects that simplicity.
Deployment Considerations:
- The 1224A requires an active Simplebus loop (controller and at least one handset or video station already in place). You cannot install the 1224A as your first Simplebus component; it's an expansion module only.
- Bus cable runs longer than 500 meters may experience signal attenuation on very old twisted-pair cabling — field test before committing to conduit runs in large campuses. Comelit publishes maximum bus length specs; request them before design.
- The unit itself is un-powered (it draws 12V via bus); installation requires only a single RJ-connector termination. But ensure your Simplebus controller power supply has reserve headroom — adding three 1224A units to a boundary system can push cumulative bus draw near capacity. Verify amperage budget at design phase.
- Call routing policy (which resident handsets ring when someone presses the 1224A button) is configured in the Comelit system software — there's no local dip-switch or LCD menu on the unit itself. That's good for preventing accidental misconfiguration by site staff, but it means configuration changes require a visit from the integrator or a site manager with software access.
- In properties with multiple Simplebus networks (e.g., separate systems for residential and commercial tenants), each network requires its own Simplebus controller. The 1224A cannot bridge networks — don't spec it as a solution for unified access across isolated systems.
The Comelit 1224A is the right choice for property managers and integrators building modular Simplebus deployments where standardization and low operational overhead outweigh open-systems flexibility. Explore the full Comelit catalog for handsets, video stations, and control hardware that pair with the 1224A.
