How many beam barrier pairs do I need to protect a fence line?

Divide the perimeter length by the effective range of your chosen beam product (typically 30 m for wireless SL-TNR, 100-200 m for wired twin-beam, 650 m for quad-beam). Outdoor installs derate ~30% from rated range for rain/fog margin. A 120 m fence usually needs 1-2 pairs of SL-100Q twin-beam, or 1 pair of SL-200QN.

What's the difference between twin-beam and quad-beam barriers?

Twin-beam barriers stack 2 IR beams vertically — both must trip simultaneously to alarm, eliminating false triggers from birds, leaves, and small animals. Quad-beam stacks 4 beams (typical 0.4/0.8/1.2/1.6 m heights), making it nearly impossible to crawl under or climb over without breaking the beam plane. Use quad-beam for high-security or estate perimeters.

Should I use wireless or wired beam barriers?

Wireless (Optex SL-TNR) is battery-operated and ideal for retrofit, where running cable would be expensive or destructive (existing fences, listed buildings, large gardens). Wired beams have unlimited runtime, faster response, and integrate directly into the alarm panel — preferred for new builds and high-value sites where battery maintenance is a liability.

Can I use beam barriers indoors?

Yes — indoor beam barriers excel in corridors, warehouse aisles, museum displays, and any narrow choke-point where you want a 'tripwire' detection line that ignores movement on either side. Indoor ranges hold to rated spec (no weather derating needed). For valuable items, install at multiple heights (low beam + waist + chest) to detect crawling and crouching.

How far apart should I space beam barrier pairs along a long perimeter?

Space pairs so they meet at posts/columns of your fence (typically every 30, 50, or 100 m depending on which product tier you pick). Overlap zones by ~10% at each junction so a strong fog patch or one failed unit doesn't open a gap. For perimeters over 500 m, use the SL-650QFR which provides full coverage with one pair per segment.