Surface Magnetic Door/Window Contact D20 — Grade 1, 5-Terminal, Single Reed

Introduction: Meet the Knight D20 — Compact Grade 1 Surface Magnetic Contact

The Knight D20 is a compact Grade 1 surface‑mount magnetic door/window contact designed for wired intruder and alarm panels. It offers a straightforward single‑reed closed‑loop detection solution in a small profile package, making it suitable for basic residential and light commercial installations. The D20 is a cost‑effective option for projects that require a reliable magnetic contact without advanced tamper features or high‑security certification.

Key features at a glance:

• Grade 1 security classification for basic/low‑risk installations.
• Single‑reed, closed‑loop contact with approximately 20 mm operating (make) gap.
• Five screw terminals (two dedicated for the reed switch, three spare brass terminals for custom wiring).
• Surface‑mount small profile form factor — suitable for standard doors and windows.
• Supplied with fixing screws; no integral tamper (microswitch) fitted.

Detailed specifications and benefits

The D20’s specifications are intentionally simple. It’s built to serve as a basic magnetic contact that connects to a wired alarm panel using traditional closed‑loop wiring. Below is a summary of its principal specifications and the practical benefits those specifications provide.

• Model:D20
• Dimensions:Approximately 67 × 14 × 12–13 mm for the combined contact and magnet — a small profile suited for most frame and door styles.
• Material:Polystyrene body — lightweight and economical for indoor applications.
• Environmental class:Class II – indoor controlled environments.
• Finish/variants:Available in white (D20) and brown (D20B) to match common door or frame colours.

Benefits: The compact size and simple plastic construction make the D20 easy to install in tight locations and suitable for interior doors and windows where exposure to harsh environmental conditions is limited.

• Contact type:Single‑reed, closed loop.
• Terminals:Five screw terminals — two nickel‑plated for the reed connection and three spare brass terminals that can be used for custom wiring or bridging depending on panel requirements.
• Operating (make) gap:Approximately 20 mm (note: gap performance may be affected by nearby ferrous materials or mounting orientation).
• Contact plating:Rhodium reported on some distributor pages (useful for corrosion resistance and reliable switching).
• Electrical ratings (distributor‑listed):Approx. 0.5 A input current; distributor pages list 100 V DC / 120 V AC values, but these should be treated cautiously and verified on official datasheets.

Benefits: The single‑reed closed loop is a proven, low‑complexity detection method offering straightforward wiring into most alarm control panels. The additional spare terminals provide flexibility during installation and when adding end‑of‑line (EOL) resistors or tamper circuits at the panel.

• Security grade:Grade 1 — suitable for basic security needs and low‑risk applications.
• Tamper:No integral case tamper (no microswitch) — meaning case tamper detection must be handled elsewhere if required.
• Certifications:Insufficient data in supplied information — consult Knight/authorised distributor datasheet for official certification details and full electrical ratings.

Benefits and caveats: For many domestic and light commercial uses the D20’s Grade 1 rating and small form factor are a match; however, installations that require tamper detection, higher security ratings (Grade 2/3), or outdoor/environmentally exposed mounting should select a different product or additional hardware to meet those needs.

Use cases and scenarios where the D20 excels

The D20 fits well into a number of practical situations where simplicity, low cost, and unobtrusive appearance are priorities. Typical use cases include:

• Residential security systems:Interior and exterior doors (when sheltered) and windows in homes where the primary requirement is basic intrusion detection tied to a wired alarm panel.
• Small offices and retail outlets:Internal office doors, storeroom doors, and basic perimeter windows in low‑risk commercial environments.
• Temporary or low‑value installations:Short‑term leased premises or locations where frequent replacement/maintenance is acceptable due to the low unit cost.
• Supplementary monitoring:Where primary security is provided by more advanced sensors, the D20 can serve as a secondary or zone sensor to increase coverage without significant cost.

Why it excels here: The combination of a small profile, straightforward wiring, and low suggested retail price (suggested price: approximately $2.99 per unit) makes the D20 a practical choice where budget and unobtrusiveness matter more than advanced features like tamper detection or weatherproofing.

Comparisons with similar products

It is useful to compare the D20 with other magnetic contacts on the market to identify where it stands out and where alternative products are preferable.

• Recessed contacts sit inside the door or frame and are harder to tamper with or spot visually. The D20 is surface‑mount and therefore more visible and easier to access, which may be less desirable for high‑security applications.
• Recessed types typically require routing or drilling into frames; the D20’s surface mounting is quicker and simpler to fit, especially on standard frames.

• Contacts with integral microswitch tamper detection provide case‑open alerts. The D20 does not include a tamper switch, so installations requiring tamper monitoring must add tamper detection at the control panel or choose a different contact.
• If anti‑tamper is a project requirement, the D20 is not the ideal choice despite its cost advantage.

• Higher grade contacts are designed and tested for more demanding security applications, often with stricter tolerance, durability, and additional features. The D20’s Grade 1 rating means it is intended for basic protection rather than high‑security sites.
• For commercial sites with higher asset value or regulated security requirements, invest in Grade 2 or 3 rated contacts instead of a Grade 1 unit like the D20.

• Wireless contacts are easier to install where running cables is difficult. The D20 requires wired connections to an alarm panel, which can be advantageous for reliability but less convenient for retrofits without wiring access.
• Battery‑free wired contacts like the D20 avoid battery replacement cycles and RF interference concerns that can affect wireless units.

Customer feedback and testimonials

No verified public customer testimonials were provided with the supplied product information. Where direct user reviews are not available, typical installer feedback and likely customer impressions include:

• "Easy to install and inexpensive" — installers appreciate the small footprint and simple screw fitment for quick deployment on interior doors.
• "Perfect for basic zones" — system integrators often use Grade 1 contacts for secondary or low‑risk zones where cost control is important.
• "Lacks tamper detection" — a common note for projects that require tamper monitoring; installers will often supplement the D20 with panel‑level tamper circuits or choose a different model when tamper is mandatory.

For authoritative customer reviews, check distributor listings and independent security forums or request installer references from your supplier.

Installation notes, pricing and procurement

The D20 is supplied with fixing screws and should be installed by a competent person or qualified installer. Follow your alarm panel manufacturer’s wiring practice and local regulations. Verify polarity and end‑of‑line resistor (EOL) arrangements as required by your control panel. Official certifications and detailed electrical ratings should be confirmed from the Knight datasheet before large‑scale procurement.

Cost perspective:With a low suggested retail price (approximately $2.99 per unit) and modest cost price (approx. $2.40 as supplied), the D20 is positioned as an economical choice for budget‑sensitive installations. Note that no warranty information was included in the supplied data — confirm warranty and returns policy with your distributor before purchase.

Conclusion: Why the Knight D20 is a good choice for basic security needs

The Knight D20 Grade 1 surface magnetic contact delivers a compact, no‑frills solution for wired alarm panels where basic door/window monitoring is required. Its small profile, simple screw‑terminal wiring, and low price point make it ideal for domestic settings, small businesses, and supplementary zone coverage in larger systems. While it lacks tamper detection and higher security grading, those trade‑offs are consistent with its market positioning: an affordable, easy‑to‑install closed‑loop contact for low‑risk applications.

If you need a durable, tamper‑protected, or outdoor‑rated sensor, consider upgrading to higher‑grade or tamper‑equipped models. For straightforward interior zones where reliability and cost efficiency matter most, the D20 remains a practical and effective choice — provided you verify official datasheet ratings and certification with Knight or an authorised distributor prior to installation.