# 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://live-roll2roll.pantheonsite.io/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 LLC, headquartered in Stillwater, Oklahoma, manufactures patented fiber-optic web position sensors and web guiding systems for roll-to-roll manufacturing. Products include ODC edge sensors (48mm to 960mm), 1DC all-in-one sensors, SCU-series controllers, and complete web guide systems.

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