USB Redirection

With USB Redirection, the signotec signature pad is passed through completely into the remote session as a USB device. On the server, the pad appears as if it were connected locally; the USB data stream is transported through the remote protocol. Citrix refers to this feature as Generic USB Redirection; Microsoft RDP uses the term USB device redirection (historically also RemoteFX USB Redirection).

This variant requires no signotec-specific components and is therefore attractive in environments where driver deployment is not possible. However, based on the experience of signotec and many customers, it is the weakest of the options documented here — especially with Microsoft RDP. If one of the other connection methods can be used, it should be preferred. A comparison of the options can be found under Comparison of Options.

How It Works

The client's USB stack does not pass the pad to the local operating system, but to the Citrix or RDP client. This tunnels the USB communication through the remote protocol. On the server, the pad is detected by the local USB stack there and made available to an application. From the server application's perspective, the pad behaves identically to a locally connected device.

Since the raw USB frames are transported over the network, this variant is sensitive to latency, bandwidth, and session interruptions. When the session reconnects, the USB device is re-enumerated, which, depending on the application, can lead to a brief disconnection from the pad.

Requirements

• signotec signature pad in the USB variant (item number ending in U100)

• PC or thin client with Citrix Workspace App or Microsoft Remote Desktop Client

• USB redirection enabled in the remote protocol (Citrix policy or RDP Group Policy)

• Administrative privileges for configuring the policies

Devices in the FT100 variant can in principle also be connected via USB Redirection, since the integrated FTDI chip appears to the client as a USB device. In this case, however, the Virtual Serial Connection is the more direct and stable approach.

Configuration in Citrix

Citrix's default rules do not automatically allow input devices (HID class) in many configurations. For signotec signature pads, an explicit allow rule is therefore usually required. The rules follow the pattern Allow: or Deny: followed by any combination of tags (VID, PID, REL, Class, SubClass, Prot). For details on the full syntax, see the Citrix documentation.

Option 1 — Allow All signotec Pads

For most environments, it is sufficient to allow all devices from the manufacturer signotec. signotec's Vendor ID (VID) is 2133:

Allow: VID=2133 # signotec Unterschriftenpads

Option 2 — Allow Only Specific Models

If redirection is to be restricted to specific pad models, the Product ID (PID) of the respective model is specified in addition to the VID. The product IDs of the current signotec pads:

Example of a targeted allow rule for signotec Sigma and signotec Delta:

Allow: VID=2133 PID=0001 # signotec Sigma
Allow: VID=2133 PID=0015 # signotec Delta

If additional pad models are used, add a separate rule for each model.

Additionally, the Client USB device redirection – Auto connect policy can be enabled so that the pad connects automatically when the session starts.

Configuration in RDP

USB redirection over RDP is still listed in Microsoft's tools under the historical name RemoteFX USB Redirection — even after Microsoft discontinued RemoteFX vGPU in 2020. USB redirection itself remains part of RDP.

It is enabled via Group Policy on the client:

Computer Configuration → Administrative Templates → Windows Components → Remote Desktop Services → Remote Desktop Connection Client → RemoteFX USB Device Redirection

Here, set the policy Allow RDP redirection of other supported RemoteFX USB devices from this computer to Enabled. The policy options let you choose whether redirection is available to administrators and/or users.

After enabling the policy and restarting the client, the pad becomes available for selection in the Remote Desktop client under Local Resources → Local devices and resources → More. Checking the box for the device redirects it into the session.

Verification

After enabling USB redirection, the pad appears in the remote session in Device Manager — for the U100 variant as a USB input device, for the FT100 variant as a USB-to-serial converter with an assigned COM port. A signotec-compatible application in the session (e.g., signoSign/2 or a line-of-business application using the signoPAD API) must then be able to address the pad.

If you experience issues, check in this order: detection of the pad on the client (Device Manager), USB redirection enabled in the remote protocol, correct VID/PID in the Citrix rule or device selection in the Remote Desktop client, and detection of the pad in the server session.

If the connection to the pad drops after a session reconnect, this is not a configuration error but a known behavior of USB Redirection: the device is re-enumerated on reconnect. In this case, the application must re-establish the connection to the pad.