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Electronics people: why are there any components in this at all? If it's just about disconnecting certain pins, couldn't it just pass the power lines through an

Electronics people: why are there any components in this at all? If it's just about disconnecting certain pins, couldn't it just pass the power lines through and be half the size without a PCB at all? For example, it could easily be a cable missing two wires, right? (Note: I'm an idiot when it comes to electronics, so I'm genuinely interested.)

xg15 12y ago
According to the USB spec, a device must complete a protocol handshake and declare a desired voltage level before the host is allowed to supply anything more than a minimum voltage. In case of the USB condom, this handshake would have to be executed by the condom. I'm not sure how widely implemented this behavior is for "dumb" USB chargers though, as opposed to actual hosts though. But it might be that they want to preserve compatibility with actual hosts, in case that you i.e. want to charge on a public PC. Or they want to make sure that even if your charger is actually a disguised malicious device, you can still use it as a charger, which would be kinda ironic.
- lockedusb 12y ago
  That's correct. LockedUSB adapter disconnect the data lines however it have an internal controller that still negotiate and complete the USB handshakes so the device can charger faster while being safe. http://www.lockedusb.com http://www.lockedusb.com
maaaats 12y ago
Maybe some devices don't charge at max rate when they sense something "wrong" with the cable. Or the other way around, a computer may not deliver power if it doesn't sense anything actually connected to the power. Just speculation.
mbell 12y ago
The USB spec identifies different types of charging ports based on the resistance / voltage connected to the data pins. Here's a chart with the USB spec (on the ends) and a couple manufacturer variants: http://i.stack.imgur.com/gWODO.jpg http://i.stack.imgur.com/gWODO.jpg
- deleted 12y ago
  [deleted]

xg15 12y ago

According to the USB spec, a device must complete a protocol handshake and declare a desired voltage level before the host is allowed to supply anything more than a minimum voltage. In case of the USB condom, this handshake would have to be executed by the condom. I'm not sure how widely implemented this behavior is for "dumb" USB chargers though, as opposed to actual hosts though. But it might be that they want to preserve compatibility with actual hosts, in case that you i.e. want to charge on a public PC. Or they want to make sure that even if your charger is actually a disguised malicious device, you can still use it as a charger, which would be kinda ironic.

lockedusb 12y ago
That's correct. LockedUSB adapter disconnect the data lines however it have an internal controller that still negotiate and complete the USB handshakes so the device can charger faster while being safe. http://www.lockedusb.com http://www.lockedusb.com

maaaats 12y ago

Maybe some devices don't charge at max rate when they sense something "wrong" with the cable. Or the other way around, a computer may not deliver power if it doesn't sense anything actually connected to the power. Just speculation.

mbell 12y ago

The USB spec identifies different types of charging ports based on the resistance / voltage connected to the data pins. Here's a chart with the USB spec (on the ends) and a couple manufacturer variants: http://i.stack.imgur.com/gWODO.jpg http://i.stack.imgur.com/gWODO.jpg

deleted 12y ago
[deleted]