A very useful device not only for makers.
The four lines 5V,GND,D+,D- can be individually switched ON or OFF (connected or disconnected).
Look at the pictures, it's pretty self-explanatory...

Usecase 1:

Charging (or power supplying) a device (e.g. your mobile / mp3-player / camera) with an "unknown" PC or the PC in your office/company/at your employer.
You don't know if this PC "scans" all your private and confidential data,
you don't know if this PC is "infected" with some virus or malware !
Simply switch off the 2 data-lines (D+ and D-) on the USB-Helper and you are protected.

Usecase 2:

Sometimes you want to communicate with a device but without connecting the 5V from the PC.
(quite often the 5V-supply from a PC is very noisy, with voltage spikes or some humming occurs...)
examples:
-- communicating with a microcontroller system that has it's own power supply (3.3V / or own 5V-System)
-- using USB audio systems (e.g. external D/A-converter) with own power supply without "injecting" noises and humming from the PC.
Simply switch off the 5V-line on the USB-Helper and you are ready to go.
(in some scenarios even the GND switch can be disconnected as well, you have to try)

Specifications:

• the four lines 5V,GND,D+,D- can be individually switched ON or OFF (connected or disconnected)
• USB "Type A" male and female connector
• compatible with USB 1.0 / USB 2.0 devices
• compatible with Low Speed [1,5 Mbit/s], Full Speed [12 Mbit/s], Hi-Speed [480 Mbit/s] devices
• the (special heavy-duty) DIP-switch is capable of switching and holding a load of 500mA
• a transparent heat shrink tube is used as protection against short circuit
• dimensions assembled: 50,9mm x 16,6mm x 12,5mm (length x width x height)
• dimensions bare PCB only: 30,1mm x 16,6mm x 1,7mm (length x width x height)
  

Scope of delivery:

you will get a kit which consists of the following parts (see pictures):

• 1pc. bare PCB
• 1pc. DIP-switch (heavy-duty/500mA)
• 1pc. USB connector plug angled THT
• 1pc. USB connector socket angled THT
• 1pc. of heat shrink tube transparent 35mm

This is open source hardware in terms of the definitions of oshwa.org