Output count, detector-input capacity and communication interfaces are separate specifications. Check independently switched signal circuits and their loads against the approved phase and signal plan, then verify detector inputs, communication functions and cabinet expansion space for the selected model.
Output count comparison
| Output count | Typical use | Cabinet size | Detector inputs |
|---|---|---|---|
| 6 outputs | Very small or temporary sites, single direction | Compact pole-mount | 0-2 |
| 22 outputs | 3- or 4-way urban intersections without arrows | Standard ground-mount cabinet | 4-8 |
| 44 outputs | 4-way intersections with arrows, pedestrian, bicycle | Full-size cabinet | 8-16 |
| 56 outputs | Complex intersections, corridors, smart control | Full-size with expansion panel | 16-32 |
1. What a controller output actually does
Count outputs from the approved wiring and I/O schedule: each independently switched signal circuit requires an appropriate output. Multiple lamps may share a circuit only where the design and electrical ratings permit. Countdown interfaces, detector inputs and communication ports must be specified separately; lamp or head count alone does not establish output capacity.
Output count is not the same as phase count. A phase is a movement group that runs green together; the outputs are the hardware channels that switch the lamps for every phase, plus any overlaps and pedestrian signals. A small intersection may run four phases on a 22-output controller with spares; a complex intersection with turn arrows, pedestrian phases and bicycle signals often needs 44 or 56 outputs.
2. When 22 outputs are enough
A smaller controller may suit a simple intersection if the approved circuit schedule, electrical loads and required reserve fit its documented capacity. Count independently switched vehicle and pedestrian circuits, accounting for permitted shared wiring; do not select capacity from the number of approaches alone.
Choose 22 outputs when the intersection has no dedicated turn arrows (or shares a permissive phase), pedestrian phases are limited to one or two crossings, detection is limited to one or two critical approaches, and the project budget prefers a smaller, simpler controller. If the controller already runs an actuated plan with loop or video detection on every approach, 22 outputs is the smallest count worth specifying. For anything smaller, fixed-time control on a 6-output box is more economical.
3. When 44-56 outputs are needed
Once you add turn arrows, bicycle signals, lane-control signals, multiple pedestrian phases or transit signal priority, the output count climbs fast. A 4-way intersection with protected left turns, pedestrian phases on every leg and bicycle signals on two legs can use 30 outputs before any spare capacity is reserved. A 56-output controller is then the safer choice, because it leaves spare outputs for future phases, additional detection and communication modules.
For additional arrows, pedestrian signals or bicycle signals, derive the required independently switched circuits from the approved phase plan. Compare that requirement and the planned reserve with the proposed controller capacities. Coordination, priority and remote monitoring also require separately verified software and communication capabilities.
4. Spare capacity and future expansion
Set the spare-output allowance from the approved expansion plan, maintenance strategy and hardware limits; no fixed percentage suits every site. Reserve detector inputs, communication interfaces and software capacity separately from switched signal outputs.
If every available output is allocated at commissioning, check whether the approved design needs expansion or maintenance reserve. A larger controller is justified only when the documented circuit count, reserve or electrical limits require it.
5. Matching outputs to cabinet wiring and terminals
The output count drives the cabinet layout. A 22-output controller usually fits in a smaller ground-mount cabinet with one output panel. A 44 or 56 output controller typically uses a larger cabinet with separate output panels, conflict monitor, detector rack and power supply. Confirm the cabinet terminal schedule matches the controller outputs before ordering — an off-the-shelf cabinet with the wrong terminal layout is a costly rework.
Also confirm the conflict monitor channels match the number of conflicting greens, detector inputs are sufficient for the planned detection design, communication ports (RS-232, RS-485, Ethernet, fibre) match the central system, and surge protection and power supply are sized for the cabinet load.
6. Detection inputs vs outputs
Buyers often confuse outputs with detection inputs. They are different. Outputs are switched channels that drive signal lamps. Detector inputs are the channels that receive calls from loops, video cameras, radar or push buttons. A 22-output controller may have 8 detector inputs; a 56-output controller may have 32. Match the detector input count to the detection design separately from the output count.
For an actuated intersection with detection on every approach, plan for at least 2 detector inputs per approach (advance loop and stop-line loop), plus inputs for pedestrian push buttons and emergency vehicle preemption.
7. RFQ checklist for output count
Before requesting a quotation, send the supplier the intersection layout and approach count, the number and type of signal heads (ball, arrow, pedestrian, bicycle), detector type and count per approach, pedestrian push button and audible signal plan, communication requirement (central system, remote monitoring, none), cabinet standard (NEMA, ITE, GB25280), and the spare output target (15-20% minimum). This lets the supplier quote a 22, 44 or 56 output controller with the correct cabinet, conflict monitor and detector rack in one proposal.
Frequently asked questions
How do I know how many outputs my intersection needs?
Count every signal indication the controller must switch: red, yellow and green for each vehicle head, plus arrows, pedestrian, bicycle, lane-control and countdown indications. Add detector inputs separately. If the total is below 18, a 22-output controller is the smallest practical choice; if it is above 30, plan for 44 or 56 outputs.
Is a 56-output controller always better than a 22-output controller?
No. A larger controller costs more and uses more cabinet space. For a simple 4-way intersection with no arrows, a 22-output controller is the economical choice. The 56-output box earns its price only when the design uses the additional outputs.
Can I add outputs to a 22-output controller later?
Output expansion depends on the controller architecture, output hardware, conflict monitoring, cabinet wiring and power capacity. Confirm whether the selected system supports an upgrade or requires replacement. Determine spare capacity from the approved future signal and load plan rather than a universal percentage.
How many detector inputs do I need?
Determine detector inputs from the approved detection plan, including stop-line, advance, pedestrian-button and preemption needs where required. Confirm available channels and interface types for the selected controller; output count does not determine detector capacity.
Do I need a different cabinet for 44 or 56 outputs?
Usually yes. A 44 or 56 output controller needs a larger ground-mount cabinet with separate output panels, a detector rack and a power supply sized for the load. Confirm the cabinet terminal schedule matches the controller outputs before ordering.
What about solar wireless controllers?
Solar wireless controller capacity should follow the site’s independently switched outputs, electrical loads and power budget. Larger or coordinated projects also require verification of the master/slave architecture, communication links and supported network size for the selected models.
Relevant GAOQIAO products
These public GAOQIAO catalogue pages are related to the guide. Open them for the representative description, then confirm the latest drawing and configuration before ordering.
- Traffic signal controllersWired and solar controllers with 6, 22, 44 and 56 output options.
- Wired traffic signal controllers22-output and 56-output controllers matched to NEMA and ITE cabinets.
- Traffic signal controller solutionsSelection guide for wired, wireless and solar controller systems.
- Solar wireless controllers6 to 22 output solar controllers for off-grid and temporary sites.