HC15 and HC25
Edited by the Electronicstalk Editorial Team on 10 September 2007
The Siemens HC15 and HC25 from TDC allow data to be transmitted and received at up to three times the speed of ISDN

Integrated Services Digital Network (ISDN) is a circuit-switched telephone network system, designed to allow digital transmission of voice and data over ordinary telephone copper wires, resulting in better quality and higher data speeds than are available with analog "Plain Old Telephone Service (POTS)". More broadly, ISDN is a set of protocols for establishing and breaking circuit switched connections, and for advanced call features for the user. It was introduced in the late 1980s. In a videoconference, ISDN provides simultaneous voice, video, and text transmission between individual desktop videoconferencing systems and group videoconferencing systems.

TDC has released two compact, High-Speed Downlink Packet Access (HSDPA) modules- yields downlink data rates up to 14 Mbps and boosts capacity in 3G networks-, offering faster transmission of data with speeds up to 3.6 Mbit/s. They provide high-bandwidth data communication services such as broadband internet, email access, and video and music streaming on portable devices.

The Siemens HC15 and HC25 from TDC allow data to be transmitted and received at up to three times the speed of ISDN.

Both modules support voice, fax, SMS and Circuit Switched Data (CSD), enabling them to be used as a modem for PDAs, laptops and other devices via infra-red ports or data cables.
The HC15 is a single-band 3G device supporting 2100 MHz and dual-band operation on 900/1800 MHz for EDGE/GPRS and GSM.

The HC25 is configured for worldwide use and offers 3G on 850/1900/2100 MHz and EDGE/GPRS/GSM on 850/900/1800/1900 MHz.

The HC25 also incorporates a GPS receiver to fulfill the requirements of US directive E911.
The HC15 and HC25 modules measure 34 x 50 x 4.5 mm and weigh less than
 10 g, making them easy to integrate into compact designs.

The modules interface with the host applications via a USB 2.0 slave interface.
USB drivers for Windows XP are included, as well as Microsoft RIL/NDIS drivers, for Windows Mobile 5 and its successor.

The normal operation temperature range is -20ºC to +65ºC.
Intelligent power-saving modes are included to minimize current consumption

References
http://www.electronicstalk.com/news/tdc/tdc140.html
http://en.wikipedia.org/wiki/Integrated_Services_Digital_Network