Installing an AMBIR scanner in Citrix:
TWAIN vs. USB redirection
Citrix supports two methods for connecting an AMBIR scanner to a virtual session. For nearly every healthcare workflow, TWAIN redirection is the recommended choice — lower latency, smaller bandwidth footprint, and resilient on shared WOW carts and thin clients.
Use TWAIN redirection.
TWAIN redirection compresses the scanned image on the client and sends only the bitmap to the session — not the raw, high-bandwidth USB packet stream. The result is a faster scan, less network load, and a far better experience on thin clients, WOW carts, and remote endpoints.
Reserve USB (Generic) redirection for cases where the EMR or capture application cannot use a TWAIN driver — it is rare, and almost always slower over WAN.
How the two redirection methods compare
Recommended:
Where the driver runs
Recommended:
Recommended:
Low — only compressed image data on the wire. Compression level is configurable via Citrix policy.
High — raw USB traffic, sustained for the full duration of the scan.
Recommended:
Generic USB Redirection
Recommended:
Generic USB Redirection
Recommended:
Generic USB Redirection
Recommended:
Generic USB Redirection
Recommended:
All current AMBIR scanners — sheetfed (DS690GT, DS687, PS670ST, PS667, DS490, PS600) and ADF (DS820ix, DS830ix, DS340, DS1060).
Generic USB Redirection
Same hardware; depends on whether the in-session app needs raw USB.
TWAIN Setup
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Overview
When you log into a Citrix Virtual App or Desktop, your applications are running on a remote server (the VDA), not on the PC in front of you. Redirection is how Citrix exposes a peripheral that’s plugged into your PC — like an AMBIR scanner — to the application running in the session.
For scanners, Citrix offers two methods: TWAIN redirection (a dedicated, optimized channel for image capture) and Generic USB redirection (which forwards raw USB traffic across the network). The choice has a big impact on speed, bandwidth, and reliability.
TWAIN redirection, in nearly every case. All AMBIR scanners — sheetfed card/document models and ADF models alike — ship with TWAIN-compliant drivers, and Epic, Cerner, NextGen, athenahealth, eClinicalWorks, and other major EMRs all use TWAIN to acquire scans. There’s no functional reason to fall back to Generic USB redirection unless your capture application explicitly requires raw USB access.
Best Practice — Standardize on TWAIN redirection across your whole Citrix estate. Use Generic USB only as a per-user exception for the rare application that doesn’t support TWAIN.
The two methods send fundamentally different things across the wire:
TWAIN redirection — The TWAIN driver runs locally on your PC. Citrix forwards only the resulting compressed bitmap to the VDA — typically a few hundred KB per card scan.
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On a clean LAN you may not notice the difference. On a WAN link, a busy WiFi network, a thin client, or a WOW (Workstation on Wheels) cart, the USB pass-through approach can stall, time out, or feel sluggish. TWAIN keeps the noisy, chatty work local and only sends the finished image.
Yes — AMBIR is a Citrix Ready partner, and all current AMBIR scanners — sheetfed (DS690GT/nScan 690gt, DS687, PS670ST/nScan 670gt, PS667, DS490/ImageScan Pro 490i, PS600/TravelScan Pro 600) and ADF (DS820ix, DS830ix, DS340, DS1060) — are validated against Citrix Virtual Apps and Desktops via TWAIN redirection. Look for the Citrix Ready badge on AMBIR product pages and in the footer of this article.
Requirements
Per current Citrix documentation, TWAIN redirection requires:
- Control plane: Citrix Virtual Apps and Desktops 1912 or later, or Citrix DaaS.
- VDA / session host: Windows 10 1809+, Windows 11, or Windows Server 2022+; VDA version 1912 or later.
- Endpoint: Windows 10 1809+ or Windows 11 with Citrix Workspace app 1912 or later.
- Scanner driver: AMBIR TWAIN driver installed on the local endpoint (not the VDA).
For 64-bit scanning applications running in the session, the 64-bit TWAIN Data Source Manager (twaindsm.dll) must be present in System32 on the VDA. Windows does not pre-install it. If your EMR or capture app doesn’t bundle it, request the file from your application vendor and copy it manually.
Yes. TWAIN redirection is on by default in Citrix Virtual Apps and Desktops. The two policy settings to know are Client TWAIN device redirection (enable/disable) and TWAIN compression level (controls how aggressively the bitmap is compressed before transit). If your environment was hardened with a custom policy template, double-check that TWAIN redirection wasn’t disabled site-wide.
Yes — both on the local endpoint (to install the AMBIR TWAIN driver) and, for one-time policy changes, on the Citrix Delivery Controller. End users do not need admin rights to scan once setup is complete. If you don’t have local admin rights on the endpoint, your IT department can push the AMBIR driver via SCCM, Intune, or your standard endpoint management tool.
Setup TWAIN
Setting up TWAIN redirection
Install the AMBIR driver on the local endpoint only — do not install it inside the Citrix session. Then verify Citrix policy and test from within the session.
- Confirm policy. In Citrix Studio, verify that Client TWAIN device redirection is set to Allowed for the delivery group serving the user. Optionally set TWAIN compression level (Low / Medium / High) — Medium is a good default; raise it for WAN-heavy sites.
- Download the AMBIR driver on the endpoint. Go to ambir.com/all-ambir-drivers and pick your model (DS690GT, DS687, PS670ST, PS667, DS490, or PS600). Install the driver before plugging in the scanner.
- Plug the scanner in. Connect the USB cable directly to the endpoint — not through a USB hub or docking station. AMBIR sheetfed scanners are USB-powered, so no separate AC adapter is needed.
- Do NOT install the driver on the VDA. With TWAIN redirection, the driver lives on the endpoint. Installing it on the VDA is unnecessary and can cause Windows to claim the device locally instead of forwarding the TWAIN call.
- Launch your session and test. Open your EMR (or Twacker, the Citrix-recommended TWAIN test tool) inside the session, choose File → Select Source, pick the AMBIR scanner from the list, and run an acquire. The card scan should return in 1–3 seconds.
If your workflow is “scan and save to a folder/cloud,” you can install AmbirScan on the endpoint and use it directly — no Citrix involvement needed for the scan itself. AmbirScan supports local file, Google Drive, OneDrive, Dropbox, and SharePoint as destinations.
If you need the scan to land inside a Citrix-published EMR (Epic, Cerner, NextGen, eClinicalWorks, etc.), you do not install AmbirScan in the session. Just install the AMBIR driver on the endpoint, let Citrix’s TWAIN redirection forward the scan into the EMR’s TWAIN dialog, and the EMR handles the file.
Important: athenahealth is the exception. athenahealth requires a separate application called AmbirScan for athenahealth (AS4A). Do not follow the standard install steps — go to ambir.com/athenahealth-setup for athenahealth-specific instructions.
Yes. Citrix recommends Twacker, the official TWAIN reference test app from the TWAIN Working Group. Install it on the VDA, launch it inside a Citrix session, and run File → Select Source → [your AMBIR scanner] → Acquire. If Twacker scans cleanly, your Citrix setup is correctly configured for TWAIN redirection and the issue lies elsewhere (typically the EMR’s TWAIN integration).
Setup USB
Use it only when the in-session application cannot use a TWAIN driver — for example, an older or specialized capture app that’s hard-coded to raw USB. This is rare for healthcare scanning. If you’re not certain, default to TWAIN.
Important: Generic USB redirection forwards every USB packet across the network. On WAN links or thin clients, scanning will be visibly slower than TWAIN redirection, and a single dropped packet can fail the scan. Treat USB redirection as the exception, not the rule.
- In Citrix Studio, set Client USB device redirection to Allowed and add a USB redirection rule that matches the AMBIR scanner’s vendor / product ID. Out of the box, Citrix’s default rules deny most imaging-class devices — you must add an explicit allow rule.
- Disable TWAIN redirection for that delivery group, or it will take precedence.
- Install the AMBIR driver on the VDA (the session host), not the endpoint. With USB redirection, the driver runs inside the virtual session.
- Connect the scanner on the endpoint. In Citrix Workspace app’s device toolbar, manually redirect the scanner to the session.
- Verify in the session. Open Device Manager inside the Citrix desktop — the AMBIR scanner should appear there, not on the local endpoint.
No — for a given scan, the scanner is claimed either by TWAIN redirection or by USB redirection, not both. If both are enabled, USB redirection wins and you lose the bandwidth and latency benefits of TWAIN. Pick one method per delivery group.
- Confirm Client TWAIN device redirection is Allowed in the active Citrix policy for that delivery group.
- Verify the AMBIR driver is installed on the endpoint and the scanner appears in local Windows Device Manager.
- For 64-bit EMRs, confirm twaindsm.dll is in C:\Windows\System32 on the VDA.
- Restart the Citrix session (full log off, not disconnect) so the virtual channel re-initializes.
- Try a different USB port on the endpoint — connect directly, not through a USB hub or docking station.
- Confirm you’re on TWAIN redirection, not USB redirection. USB redirection over WAN is the most common cause of slow scans.
- Raise the TWAIN compression level Citrix policy from Low to Medium or High to reduce payload size.
- Drop scan resolution to 300 DPI for ID and insurance cards — 600 DPI quadruples the file size with no readability gain.
- For document workflows, enable Blank Page Removal and Auto Crop in AmbirScan or in your EMR’s TWAIN dialog.
Windows feature updates and Citrix Workspace app updates can both reset device drivers. Refresh the AMBIR driver:
- On the endpoint, open Control Panel → Programs and uninstall the existing AMBIR driver.
- Reboot the endpoint.
- Download the latest driver from ambir.com/all-ambir-drivers and reinstall.
- Plug the scanner back in and re-test inside the Citrix session.