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I have a system that is a Windows 10 laptop that needs to connect to some systems using a 56k modem. The modem itself is a standard US Robotics 5686 (E, I believe) external modem. It works on other computers.

The Windows 10 laptop obviously didn't have a serial port, so I connected a Sabrent CB-9P6F USB to serial cable to the USB hub connected on that laptop. Nothing works. I can install the modem manually and choose COM4 or COM5, for instance, but I can't even query the modem. It's like it's not even connected.

Back when I tried to get it working on a Windows 98 computer with no networking support, I had fewer issues in trying to get it working than I am here.

If it was just that Windows 10 was so awful that the support for this was gone, that would be one thing, but the specifications for both the modem AND the adapter say Windows 10 is supported, so what gives? How can this be made to work, if at all?

In other words:

  • drivers are not an issue
  • modem support for Windows 10 is not an issue
  • adapter support for Windows 10 is not an issue

The adapter does show up in Device Manager as a COM port; I'm just not able to make use of it. I can add a modem manually (Windows can't automatically detect any) on that port, but it doesn't work at all.

After installing suggested fix:

Still doesn't work, unfortunately. These are the major changes I noticed: enter image description here

enter image description here

The modem is on COM4, and COM4 displays the yellow warning icon and complains that the driver was not digitally signed, etc. However, I'm not sure why this would prevent the modem from using it.

InterLinked
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1 Answers1

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The Sabrent CB-9P6F device is made by Prolific, which is the source of the problem.

The article Prolific USB To Serial Driver Code 10 Fix has an explanation for the problem:

What has happened is that there have been counterfeit “Prolific” chips coming from China. The counterfeit chips use the same Vendor ID (VID_067B) and Product ID (PID_2303) as the authentic Prolific chips. So, Prolific made a new chip and dropped all support for the old one thereby rendering the counterfeit chips unusable. Unfortunately, it renders hundreds of legacy devices using the earlier chip inoperative. Getting a working driver installed by the average user is almost impossible.

If one of these Prolific drivers gets installed to your Windows 64-bit computer then your legacy device will no longer work and will issue the generic “Code 10” error.

Or, you may get no error at all, but your device will not work.

The simplest solution would be to get a non-Prolific USB to serial cable.

If you prefer instead to get this one cable working on Windows 10, you should install an older driver.

You may find such a driver on this webpage. The version you want is "PL2303", so download the version 32/64-bit that suits your Windows version.

harrymc
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