Put-to-light in picking and sorting

Put-to-Light Picking
Put-to-Light as the second stage in two-stage order picking

Put-to-Light is a method for sorting goods with the help of luminous compartment indicators. The light signals at the put walls help the picker to quickly find his storage compartments. The Put to Light system uses the same shelf indicators as the Pick to Light system.

How does Put-to-Light work in order picking

Before starting, a batch of orders is compiled in the warehouse management system (Multi-Order-Picking). In a two-stage picking process, the goods are first picked from the warehouse in several totes. The totes are then taken to the sorting station and distributed to multiple orders using the put to light system. Depending on the solution, there are two different processes in the sortation:

1. put-to-light sorting with the same articles

If the picking system picks into the totes according to type, then there are always the same articles in a tote. For the distribution of the goods it is enough that the bin barcode is read. After that, the system turns on all the compartment displays on the sorting rack with corresponding quantities.

The order picker confirms the placement of the items on the acknowledgement button. This method is used only when the number of products is small.

2. collection boxes

In the first stage of picking, different items are first picked into the collection box. When the goods are distributed, the employee must read each article again and sort them separately. Acknowledgement at the acknowledgement button is identical. This method is slower than the first one, but gives more flexibility with a wide range of articles.

Entering the quantity into the put-to-light process

In some solutions, the items in the box can be grouped very easily (e.g. CD, DVD, etc.), which means that the removal must be done in groups and not individually.

In this case, the number of items can be entered on a screen of the sorting station. During the sorting process, the barcode only has to be read once. This saves a lot of time and money during sorting.

Sensors during acknowledgement

To improve the performance and quality of sorting, sensors are also optionally used on the compartment displays. They automatically acknowledge the placement of items into the sorting compartments, providing feedback to the position management system without the need to press the acknowledgement button. The increase in performance when using sensors is approx. +15%.

What is important in a put-to-light system?

The most important thing in a Put to Light system is the reaction time after reading the barcode. The picker must not wait for the light of the compartment display. From our experience, the response time of the system must not exceed 250ms. Our communication server (LUCA-Server) guarantees the corresponding response times without any problems.


Some of the biggest advantages of put-to-light picking include:

  • Quick orientation of the employee due to the illuminated compartment displays (short search time)
  • Direct display of the number of pieces at the storage compartment (target compartment)
  • Direct acknowledgement of the deposit at the acknowledgement button or sensor and direct response to the warehouse management system
  • Fewer errors, more performance


However, the process also has some disadvantages:

  • low flexibility due to fixed batch size (number of storage locations)
  • Relatively high investment costs (as with pick to light)


Put to Light solutions are procedures in two-stage paperless picking, in which sorting takes place in the second stage with illuminated compartment displays. In this way, it is a reverse Pick-to-Light process, in which items are not picked, but put according to the light signals. Read more about put-to-light on Wikipedia or contact us to learn more. We will be happy to advise you.

Many years of experience in paperless order picking