After redirecting the Philips speech mike as generic device in a 7.6 session we can use the record, play, pause, rewind and fast forward buttons. However we are not able to use the trackball or mouse buttons on the device.
We can also test this by redirecting the usb mouse to the session. After redirecting the mouse to generic mode/USB mode we can see that mouse does redirect but we have no functionality.
 

The solution is to upgrade to 7.15 LTSR 

or if you are using current release the feature was introduced from VDA version 7.13 onwards

https://docs.citrix.com/en-us/xenapp-and-xendesktop/7-13/whats-new.html

The information on the doc shows the following. It specifies Wacom tablet pen however this relates to mice in general as they are in the same class.

• Enhanced drawing features on Wacom tablets. Wacom drawing tablets can connect to published desktops on a remote desktop service (RDS) VM when redirected with generic USB redirection. Though you can use the tablet's pen device as a mouse device while it is redirected, we recommend that you also maintain a standard USB mouse, which is not redirected, to allow access to local client functions. The redirected device is active only inside the session and doesn't have control over the local client. Install the driver for the Wacom devices on the hosting RDS OS and the same driver must support each device connected to the server. For more information, see USB and client drive considerations.

 

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Problem Cause

This feature is not available in vda versions 7.6 - 7.12