BD Loops - Reverse Loop / Safety Loop - 4' X 6' or 3' x 7' Direct Burial Performed Loops with 40' Lead
The BD Loops RL 20-40 is a preformed direct burial inductive loop built for vehicle detection at automatic gate and access-control entrances. This model has a 20 ft perimeter loop section, a common field layout of 3 ft x 7 ft or 4 ft x 6 ft, and a 40 ft lead-in run for routing back toward the loop detector, gate operator, or control enclosure. Because the loop is already formed, the installer does not have to wind loose loop wire in the field to create the detection area. That helps keep the loop shape consistent and makes it easier to place the loop correctly before concrete, asphalt, pavers, gravel, or dirt road material is finished over it.
It is commonly used as a reverse, safety, or obstruction loop to help a compatible loop detector hold or reopen an automatic gate when a vehicle is in the protected area. The loop wire creates the inductive field, but a separate loop detector is required to power and read that field. When a vehicle enters the detection area, the detector senses the change in inductance and sends a relay or control signal to the gate operator. Correct loop sizing, placement, depth, lead-in routing, and detector setup all matter. A loop that is too small, too deep, too close to another loop, or paired with the wrong detector settings can miss vehicles or create nuisance detections.
This product is best matched by the actual loop footprint and lead-in length, not just the general driveway width. The 3 ft x 7 ft or 4 ft x 6 ft footprint is commonly selected for driveway lanes where this detection area is appropriate. The 40 ft lead-in should be long enough to reach the detector location without underground splices whenever practical. BD uses RL part numbers for 40 ft lead-in loops and EL part numbers for longer lead-in versions, so compare both the loop size and the lead length before selecting a replacement.
Compatible With
This direct burial loop may be used with any compatible inductive loop detector and gate operator control system that accepts a loop detector output.
- Typical reverse-loop and safety-loop uses include vehicle protection at slide gates, swing gates, and barrier gates where the loop detector output is wired to a safety, reverse, or hold-open input. The 40 ft lead-in is commonly used when the protected loop area is near the gate opening or roadway edge.
- Compatible with plug-in, 11-pin, DIN-rail, and cabinet-mounted loop detectors when the detector and operator wiring support the required exit, reverse, safety, hold-open, or shadow-loop function.
- Commonly used with swing gate operators, slide gate operators, barrier gate operators, telephone entry systems with gate control output, and access-control systems that rely on a gate operator loop input.
- Common detector brands used with this style of loop include EDI, Reno A&E, EMX, Diablo Controls, Nortech, Linear/OSCO, LiftMaster/Chamberlain/Elite, FAAC, Viking, HySecurity, DoorKing, Apollo/Nice, All-O-Matic, and similar detector systems when the electrical input and socket style match.
- May be used for exit, reverse, safety, hold-open, shadow-loop, or vehicle-presence functions when the loop position and detector output are set for that job.
Features & Specifications
| Manufacturer | BD Loops |
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| Product Type | Preformed Direct Burial Inductive Vehicle Detection Loop |
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| Part Number | RL 20-40 |
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| Gate Function | Reverse Loop / Safety Loop |
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| Loop Perimeter | 20 ft perimeter |
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| Common Loop Footprint | 3 ft x 7 ft or 4 ft x 6 ft |
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| Lead-In Length | 40 ft |
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| Wire / Construction | Preformed direct burial loop with jacketed lead-in and solid copper loop wire |
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| Application | Automatic gate vehicle detection, exit loop, reverse loop, safety loop, shadow loop, or access-control vehicle detection when used with the proper detector |
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| Compatible Operator Type | Swing gate, slide gate, barrier gate, and access-control systems when connected through a compatible loop detector |
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| Installation Surface | Concrete pours, asphalt paving, pavers, gravel roads, and dirt roads |
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| Detector Required | Yes. A separate inductive loop detector is required. |
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| Notes | Loop placement and detector settings must match the gate layout, driveway width, and safety requirements. |
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Also Known As / Related Part Numbers
- RL 20-40
- RL20-40
- RL-20-40
- BD RL 20-40
- BD-RL-20-40
- BD-RL20-40
- RL 20 40
- EL 20-60
- EL20-60
- BD-EL-20-60
Technician Note
The RL 20-40 is not a complete vehicle detector by itself. It is the buried sensing loop that connects to a loop detector module. Keep the lead-in protected, avoid underground splices when possible, and separate multiple loop lead-ins or set detector frequencies apart to reduce cross talk. Direct burial loops should not be treated as a substitute for required monitored photo eyes, edge sensors, or other UL 325 safety devices.
Before Ordering Checklist
- Confirm the loop size: 3 ft x 7 ft or 4 ft x 6 ft.
- Confirm the lead-in length: 40 ft.
- Confirm whether the loop will be used for exit, reverse, safety, hold-open, or shadow-loop operation.
- Confirm the detector style and voltage used by the gate operator or control cabinet.
- Confirm the loop will be installed at the proper distance from the gate, curb, other loops, and moving gate path.
- Confirm whether the job is direct burial/new surface work or an existing saw-cut roadway.
Professional Advisory
Vehicle loops are part of the gate control and safety layout, but they do not replace required entrapment protection. For commercial gates, community entrances, high-traffic driveways, or any system with unsafe gate movement, have a qualified gate technician verify the loop layout, detector wiring, and required monitored safety devices.
Important Ordering Warnings
- Do not install this direct burial loop directly in contact with hot asphalt; follow the proper sand barrier and sub-base method.
- Do not place a direct burial loop under rebar where the metal can absorb the detection field and reduce performance.
- Do not assume one loop size works for every driveway. Vehicle height, gate type, lane width, and loop depth affect detection.
- Do not bypass photo eyes, edge sensors, or monitored safety inputs to make a loop work.
Product Questions & Answers
What size is the BD Loops RL 20-40 direct burial loop?
The RL 20-40 loop is a 20 ft perimeter preformed direct burial loop. It is commonly laid out as 3 ft x 7 ft or 4 ft x 6 ft and includes a 40 ft lead-in run.
Can the BD Loops RL 20-40 be used with my gate operator?
The loop can be used with gate operators that are wired to a compatible inductive loop detector. The gate operator does not read the loop wire directly unless it has the proper detector electronics or plug-in detector installed.
Is this loop for direct burial or saw-cut installation?
This is a direct burial preformed loop for installation under new concrete, asphalt, pavers, gravel, or dirt surfaces. For an existing saw-cut roadway, use a saw-cut loop style unless the job layout specifically allows a direct burial loop.
Where is a reverse or safety loop like RL 20-40 normally placed?
A reverse or safety loop is normally placed near the gate opening or protected travel area so the loop detector can help prevent the gate from closing on a vehicle. Loop placement must avoid the moving gate path and match the operator safety input requirements.
Can I shorten the 40 ft lead-in on this loop?
Excess lead-in can usually be shortened, but avoid cutting it too short. Splicing a lead-in creates a possible failure point, especially in wet or underground conditions.
