# What happens when the printed line is intermittent, such as gaps between labels?

> The Roll-2-Roll Controller includes Loss of Contrast Logic specifically for this situation. When the sensor encounters a gap where the tracked feature disappears (such as the space between labels), the web guide holds its current position. When the sensor sees the same feature again—matching the ...

**Last updated:** 2026-02-01

**Source:** https://r2r.tech/resources/faq/what-happens-when-printed-line-intermittent-such-gaps-between-labels

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## Question

What happens when the printed line is intermittent, such as gaps between labels?

## Short Answer

Loss of Contrast Logic holds the guide position during gaps, then resumes tracking when the feature returns.

## Detailed Answer

The [Roll-2-Roll® Controller](https://r2r.tech/products/controllers) includes Loss of Contrast Logic specifically for this situation. When the sensor encounters a gap where the tracked feature disappears (such as the space between labels), the web guide holds its current position. When the sensor sees the same feature again—matching the width and hue characteristics taught during setup—tracking resumes automatically. This prevents the "hunting" or crashing behavior common with traditional line sensors.

**Category:** Technical

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## About Roll-2-Roll Technologies

Roll-2-Roll Technologies designs and manufactures patented fiber-optic web position sensors and advanced web guiding controllers — the precision measurement and control core of modern roll-to-roll manufacturing. Spun out of Oklahoma State University's Web Handling Research Center and trusted by Fortune 500 medical, battery, and nonwovens manufacturers, our patented sensors work without recalibration at ±0.1mm accuracy up to 760 mpm — typical customer outcomes are 50%+ less downtime and payback under six months. Headquartered in Stillwater, Oklahoma, our team of PhDs, controls engineers, and industry veterans extends the sensor + controller core into complete web guide systems including stepper-motor-based linear actuators (RLA, BLA, LHS).

- Website: https://r2r.tech
- Phone: +1 (888) 290-3215
- Email: sales@r2r.tech