Frequently Asked Questions – Electronic Control System

Welcome to the frequently asked questions about ARRI Pro Camera Accessories (PCA).
This FAQ pertains to ARRI Wireless Systems. Directions given are always from the operator’s point of view. This FAQ supersedes any earlier versions. If you have questions, suggestions or comments regarding this FAQ, send an email to

 1. Wireless Compact Unit WCU-4

Yes. You can use the WCU-4 with any camera, using the Universal Motor Controller UMC-3A. You can control up to three lens motors with the UMC-3A, although lens data will not be displayed on the WCU-4.
There are many different lenses on the market and we do not have an individual pre-marked ring for all of them.
We do have four pre-marked rings with metric scale and four rings with imperial scale. These eight rings can be mapped to any given lens by using the Lens Data Archive (LDA).


You would typically choose the ring marked with a close focus or minimum object distance (MOD) that is nearest to – but less than – the MOD of your lens. For example, if your lens MOD is 16”, you would choose the 14” focus ring.
Lens data is transmitted to the WCU-4 from all ALEXA cameras that have an integrated Plus module. It’s the same lens data that is embedded to the HD-SDI streams with the image files, for use in postproduction. 
Lens data is generated in the camera rather than in the WCU-4. The data gets to the camera in one of two ways:
1. From LDS lenses, via the internal lens encoders
2. From the Lens Data Archive (LDA), via the motor encoders

The Lens Data Archive is an archive that contains lens tables. Those lens tables set the raw motor encoder values in correlation to the actual lens scales.

Once you choose the right lens table from the Lens Data Archive and calibrate your lens motors, you get the same type of lens data as an LDS lens would deliver.
You can create your own lens tables for any given lens by using the ALEXA web remote.

2. Universal Motor Controller UMC-3A

You can control up to three lens motors via the UMC-3A
It does not matter which ARRI motor models (CLM-2, CLM-3 or CLM-4) you are using. You can also mix them.
To power the UMC-3A externally you need to combine two PSC cables.For further information regarding PSC cables, please see  5. PSC-Cables.
Please also see Configuration Overview UMC-3A

3. Zoom Main Unit ZMU-3A

You can connect the ZMU-3A directly to an ALEXA Plus camera with specific cables. If you do not have a Plus camera version, you should connect the ZMU-3A to the UMC-3A via cables and then the UMC-3A to your camera model.

Please see Configuration Overview ZMU-3A

Please see Configuration Overview UMC-3A

You can use the ZMU-3A wirelessly with the Wireless Zoom Extension WZE-3 (Battery NP-FM 500H and charger needed).

Please see Configuration Overview ZMU-3A


Controlled Lens Motor

The CLM-2 and CLM-4 will suit most lenses. The CLM-2 is more compact, while the CLM-4 features flexible mounting options and exceptionally quiet operation.

The CLM-3 is a very fast and strong motor that is well suited for large-diameter zoom lenses or older, stiffer lenses that require more torque.
For CLM-Accessories please see Configuration Overview Wireless System


PSC Cables

PSC means Power Supply Connector. The ARRI PSC cable system was developed for our Universal Motor Controllers (UMC), which are designed to work with many different power sources and many different cameras. To make the UMC power cable system as affordable as possible, we split it into two basic parts – both parts are required to have a complete cable system:

  • UMC-3A (or WCU-3 or ZMU-3A) to PSC (and camera) cable
  • PSC to power source cable

The benefit of the PSC cable system is flexibility at a relatively low cost. In order to use a different power source or a different camera, you only need to replace one half of the cable system.


To make the cable system as affordable and flexible as possible, we split it into two basic parts – both parts are required to have a complete cable system.

What do I want to connect -> upper part: Product to PSC connector
How do I want to power -> lower part: PSC connector to power source

Please see Configuration Overview-> WRS Cables.
For more details please also see Configuration Overview for -> UMC-3A and  ->ZMU-3A