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m Self-revert, as I've reexamined the source info and revised my analysis. |
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After that (and on every consecutive plugging) this device driver switches the mode internally, the storage device vanishes (in most cases), and a new device (like a USB [[modem]]) shows up. The [[Wireless WAN]] (WWAN) gear maker Option calls that feature "ZeroCD (TM)". With USB sniffing programs and [[libusb]] it is possible to eavesdrop the communication of the MS Windows device driver, to isolate the [[Command (computing)|command]] or action that does the switching and to reproduce the same thing under the rule of Linux or the [[BSD]] variants.<ref name="usb_modeswitch">{{Cite web|url=http://www.draisberghof.de/usb_modeswitch/|title=USB_ModeSwitch - Activating Switchable USB Devices on Linux}}</ref>
The problem with most USB [[3G]] modems is they have two modes. In one mode they are a USB flash drive and in the other mode they are a modem. Typically they only ship with Windows device drivers, sometimes [[Macintosh|Mac]] device drivers as well. In any case, they seemingly seldom, if ever, ship with Linux device drivers. What normally happens with Windows is the device starts up as a USB flash drive, the [[Computer hardware|hardware]] drivers are installed and then they are responsible for "switching" the device in to modem mode so you can use it. This "switch" is done via some codes, specific to the device, which controlling software can pass as a command to switch from disk to modem mode. The virtual CD-ROM switching utility manages the switch of mode from disk to modem, the latter disconnects any mounted disk containing software we don't care about that won't work anyway and, crucially, creates a modem port/serial device (usually {{mono|/dev/ttyUSB0}}) for the networkmanager.<ref name="3g_usb_modems ">{{Cite web|url=http://www.drupaler.co.uk/blog/installing-3g-usb-modems-linux/497|author=greg.harvey|title=Installing 3G USB Modems On Linux|date=28 April 2010|
The approach of adding Virtual CD-ROM with software drivers on 3G or storage devices has two problems: it presumably raises the cost of the device, and it may ship outdated software or even viruses. Most of the times, up-to-date drivers are anyway built into the operating systems (after all, on systems implementing the USB standard like GNU/Linux, any 3G device is a USB serial port, and any storage device is a ... USB storage device). Virtual CD-ROM on U3-compatible devices can be removed by a software tool.<ref>{{cite web|url=http://u3-tool.sourceforge.net/|title=u3_tool - Tool for controlling U3 drives|
==ZeroCD==
When a device uses the ZeroCD method means that it behaves as a USB CD-ROM when first connected, with a virtual CD-ROM inserted with the Windows device drivers and related Cosmote control program. Once the Windows device drivers are installed, a special USB command is sent to the device to “switch” it to modem mode.<ref>{{cite web|title=ZTE MF636 (Cosmote 3G USB Modem in Greece) & Linux|date=5 November 2009|
==Ozerocdoff==
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