# Multi-Unit 2x1:1

The Multi-Unit 2x1:1 case has two independent transmitters on ROVs or divers, with each transmitter on a different channel. A separate receiver tracks each transmitter. 

The position of each transmitter is updated once per second.

If a topside GPS is associated with each receiver, the absolute (latitude/longitude) position of each transmitter can be known.

The Mk II Autosync model is the only ROVL model that can operate on two channels. In order to maintain clock synchronization, all four units must surface and re-acquire the GPS signal periodically (every hour or two).

{% hint style="info" %}
The 2x1:1 case is supported by CeruleanTracker and CeruleanMap software (each pair reports to their own PC running CeruleanTracker). Additionally, users can write their own software to make of of the positional information created.
{% endhint %}

{% hint style="info" %}
If the PCs are networked together the communication between CeruleanTracker and CeruleanMap will interfere with each other. If user-generated software is used to communicate directly with receivers and process the information, then it is possible to connect both receivers to a single PC.
{% endhint %}

{% hint style="info" %}
Only one instance of CeruleanTracker can run on a single PC.
{% endhint %}

{% hint style="info" %}
Only one instance of CeruleanMap can run on a single PC.
{% endhint %}

<figure><img src="/files/rMCdM1STheiq2vroArWo" alt=""><figcaption><p>Two independent receivers, each tracking their own independent transmitter</p></figcaption></figure>


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