EC25‑EUX 4G Dongle FAQ – Deutsche Telekom VoLTE, USB Audio, Firmware

FAQs: 4G LTE Dongle with Quectel EC25-EUX Mini PCIe

Product Overview

The EXVIST 4G LTE Dongle is an industrial-grade evaluation kit that integrates a Quectel EC25-EUX Mini PCIe module with a Mini PCIe to USB Type-C adapter. It is designed for IoT/M2M applications including industrial equipment networking, Raspberry Pi projects, vehicle applications, and more.

Key Features:
  1. Quectel EC25-EUX IoT/M2M‑optimized LTE Cat 4 module
  2. Maximum data rates: 150 Mbps downlink / 50 Mbps uplink
  3. Type-C USB 3.1 connector
  4. Standard SIM card slot (drawer type)
  5. 2x 4G antennas included
  6. Industrial-grade circuit design with DC-DC power chip

Q1: What SIM card size does the drawer slot accept?

Answer: The drawer-type SIM slot accepts a Standard SIM (also known as Mini SIM, 2FF).
SIM Type
Size (mm)
Compatibility
Standard (2FF)
25 × 15 mm
✅ Direct fit
Micro (3FF)
15 × 12 mm
Requires adapter
Nano (4FF)
12.3 × 8.8 mm
Requires adapter
Notes
Recommendation: If you have a Nano or Micro SIM, please use a SIM card adapter to convert it to Standard (2FF) size before inserting

Q2: Is the EC25-EUX certified for VoLTE on Deutsche Telekom in Germany?

Answer: Yes, the EC25-EUX module holds carrier certification for Deutsche Telekom and supports VoLTE functionality.

Technical Details:

  1. Quectel documentation lists Deutsche Telekom and Vodafone as certified operators for the EC25-EUX variant.
  2. The module includes operator‑specific MBN profiles such as Commercial-DT and VF_Germany_VoLTE.

Important Considerations:

1. Hardware certification ≠ out‑of‑box operation. VoLTE depends heavily on:
  1. The specific firmware version installed.
  2. Correct MBN profile selection via AT commands.
2. If the MBN list does not contain a Deutsche Telekom entry, a firmware update may be required.

Supported Bands (EC25-EUX):

Technology
Supported Bands
LTE-FDD
B1/B3/B7/B8/B20/B28A
LTE-TDD
B38/B40/B41
WCDMA
B1/B8
GSM/EDGE
B3/B8
GNSS
GPS/GLONASS/BeiDou/Galileo/QZSS (Optional)
AT Command
Remark
AT+QGMR
# Check firmware version
AT+QMBNCFG="list"
# List available operator profiles
AT+QMBNCFG="autosel",1
# Enable automatic profile selection

Q3: Does the dongle support USB Audio (UAC) for voice calls on Linux (Asterisk + chan_quectel)?

Answer: Yes, the EC25-EUX supports USB Audio Class (UAC) when running the appropriate firmware and configured correctly.

How It Works:

The module can be configured to expose itself as a USB sound card (UAC device) to the host system, allowing ALSA on Linux to capture and play audio streams.
Required AT Commands (Community‑validated):
AT Commands
Remark
AT+QCFG="usbcfg",0x2C7C,0x0125,1,1,1,1,1,0,1
Enables UAC function in the USB configuration.
AT+QPCMV=1,2
Routes voice data to the UAC interface.

Important Notes:

  1. The UAC interface operates at 8kHz / S16 / mono.
  2. If AT+QCFG="usbcfg" returns ERROR, the firmware does not support UAC.
  3. UAC support is firmware‑dependent. Older firmware versions may lack UAC functionality.
  4. Known firmware versions with confirmed UAC support include: EC25EFAR06A21M4G, EC25EUXGAR08A19M1G (and later)

Post‑configuration Verification:

cat /proc/asound/cards
aplay -l

Q4: Can I request a specific firmware version or have UAC pre‑flashed before shipping?

Answer: We can flash specific firmware for individual orders before shipping. By default, all modules ship with the manufacturer's standard factory firmware.

Q6: Is this dongle plug‑and‑play?

Answer: No — this is not a plug‑and‑play dongle.

Required Steps:

  1. Install the corresponding drivers for the EC25-EUX module.
  2. Insert a valid SIM card with an active data/voice plan.
  3. Configure the module using AT commands as needed for your application (e.g., VoLTE, UAC).