# Inquire about using cable power and signal at the same time **URL:** \ **Category:** Cables\ **Created:** [June 24, 2021, 9:02am UTC](https://discuss.bluerobotics.com/t/inquire-about-using-cable-power-and-signal-at-the-same-time/9987 "2021-06-24T09:02:38Z")\ **Posts on this page:** 1\ **Showing post:** 2
**Author:** ![EliotBR](https://sea1.discourse-cdn.com/flex019/user_avatar/discuss.bluerobotics.com/eliotbr/32/6937_2.png) [@EliotBR](https://discuss.bluerobotics.com/u/EliotBR)\ **Post date:** [June 25, 2021, 5:40am UTC](https://discuss.bluerobotics.com/t/inquire-about-using-cable-power-and-signal-at-the-same-time/9987/2 "2021-06-25T05:40:39Z")
Hi @HanJIK, > [@HanJIK](#): > > Can Fathom ROV Tether (ROV-ready) cables be used as power cables like High-Power Tether Cable with Connectors for OTPS cables? The Fathom ROV Tether hasn’t been designed for high power use, and if you don’t already have experience with high power electronics I would strongly recommend against it without close supervision - it’s very possible to be **permanently injured or killed** by electricity in this range. **The [OTPS User Manual](https://bluerobotics.com/wp-content/uploads/2019/12/OTPS-User-Manual-46-0013-Rev-2.pdf) has several relevant warnings** about the dangers of the different parts of the system, and **you should definitely make sure you’ve at least read and understood those** before proceeding with even the design stage of a potential high-voltage tether system. > [@HanJIK](#): > > I wonder how the High-Power Tether Cable with Connectors for OTPS cable is structured so that both power and signal lines can be used at the same time. The OTPS cable structure is detailed in its [Product Description](https://bluerobotics.com/store/cables-connectors/cables/otps1kw-cab-tether-r1-vp/). Notable differences from the Fathom ROV Tether are the thicker conductors for power transmission (23 AWG) and ground connection (24 AWG) compared to the data wires (26 AWG), as well as an additional solid polyurethane rubber outer jacket to better resist abrasion and cutting. If you look in the [Technical Details tab](https://bluerobotics.com/store/cables-connectors/cables/otps1kw-cab-tether-r1-vp/#tab-technical-details) you’ll see that the cable strength and voltage ratings are also quite a bit higher for the OTPS cable. # Technical Considerations ## Maximum Electrical Ratings From a theoretical perspective any conductors are capable of carrying current, so it’s technically possible to put power through them, and a clean DC signal is unlikely to cause significant electrical noise on twisted-pair differential-signal wires. We haven’t specified a current rating for our tether wires, so as a rough indication [this resource](https://www.multicable.com/resources/reference-data/current-carrying-capacity-of-copper-conductors/) suggests 26 AWG cables with polypropylene insulation should be able to carry up to 5A at 90^\text{o}C, but when bundled as a group of 8 in a single cable that’s derated down to 3.5A. It’s possible that the internal filler and strength fibres and waterblocking compound, and the outer insulation foam, increase that thermal insulation, or could have thermal breakdown issues, so I wouldn’t suggest going that high. Similarly, while the cable is rated to 300V that’s the maximum - it’s generally a good idea to stay below that. For reference, the OTPS high-power tether is rated to 600V, and the current-rating-estimate resource I linked to suggests it could potentially take up to 6A (including grouping derating), but it’s actually used with 400V and a maximum of 4A is outputted from the OTPS. Both of those are 33% lower than the respective rating, which seems like a reasonable buffer for keeping things safe. ## Application Considerations/Potential Technical Issues I recently provided a relatively detailed outline of power conversion and transfer requirements and losses in the OTPS system [here](https://discuss.bluerobotics.com/t/inverter-generator-for-outland-power-supply/9933/2#operating-requirements-1). Of particular note is our [voltage drop calculator](https://bluerobotics.com/learn/voltage-drop-calculator/?gauge=26%20AWG&conductors=2&voltage=300%20V&length=100%20m&input=3.5%20A), which for your proposed option of using a Fathom ROV Tether would have a power transmission maximum of 890W, assuming you had a 100m tether with 300V across two pairs of 26AWG wires at 3.5A. I’m recommending power through this cable should stay below those values, so it’s very possible there wouldn’t be sufficient power transfer to use the thrusters to their full capacity (especially since that 890W then gets reduced by another 10% or so as the loss from converting down to a voltage the ROV can actually use). --- _[View the full topic](https://discuss.bluerobotics.com/t/inquire-about-using-cable-power-and-signal-at-the-same-time/9987)._