USB-B to USB-B: The Rare Legitimate Device Cable
Quick answer / TL;DR: Short answer: a B-to-B cable is used where a device's upstream port is USB-B, such as some USB 3.0 hubs, KVM switches and audio interfaces. Never substitute an A-to-A cable for a host-to-host link: without a bridge chip, two hosts both supply 5 V. Check the port labels before buying.
A patch cord is a stranded assembly: moulded boot, eight contacts, T568B.Most USB cables connect a host to a device. A B-to-B cable connects two devices, which is normally forbidden because both ends would try to supply power.
It exists for specific equipment where the upstream port is deliberately a B socket.
Legitimate Uses
| Device | Upstream port | Why B-to-B |
|---|
| USB 3.0 hub | USB-B | Upstream is B |
| KVM switch | USB-B | Device side of KVM |
| Audio interface | USB-B | Standard on many units |
| Printer | USB-B | Needs A-to-B, not B-to-B |
The printer row is the common confusion: printers have a B socket but connect to a host, so they need A-to-B.
The Host-to-Host Problem
- Two hosts both drive 5 V on the same pair
- A bridge cable contains electronics, not just wire
- A-A cables are not bridge cables
- Damage is possible on unprotected ports
Bridge cables are a distinct product with a chip in the middle. They look similar and cost more, which is the practical clue.
Real-World Applications
A rack KVM with B ports on the device side needs B-to-B cables for each computer. A printer in the same rack needs A-to-B, and mixing them up is the most common ordering error.
Standards and Verification
| Reference | Relevance |
|---|
| USB 2.0 and 3.2 | Topology and power |
| USB-IF | Connector types |
| USB bridge cables | Proprietary electronics |
Port type for a specific device is not provided in the knowledge base. Check the rear panel labelling.
Practical Notes
Label B-to-B cables distinctly. They are rare enough that they get used for the wrong job.
Related reading: usb b female coupler — blogs/news/usb-b-female-coupler
Related reading: usb to usb bridge cable — blogs/news/usb-to-usb-bridge-cable
Frequently Asked Questions
Can I connect two PCs with B-to-B?
No. Use a bridge cable.
Is A-to-A ever safe?
Not for host-to-host without a bridge.
Do printers need B-to-B?
No. They need A-to-B.
Sourcing cables for a project, a store, or a private-label line? Contact our B2B sales team for specifications, certification evidence, and volume terms – FOB and CIF options available. Request a quote or sample.
