Siemens EWSD Magnetic Tape Emulation


Siemens was founded about 150 years ago in Germany around advanced telegraph technology. The company produced it first digital telephone exchange in 1980, called the Siemens EWSD. Siemens is one of the world's largest companies, employing over 400,000 people and with operations in around countries. Siemens has continued in the telecommunications industry, most recently merging with a Nokia group to form Nokia Siemens Networks.

Installed Base

Siemens is one of the largest telecommunications companies by installed base. Some 200M EWSD lines were installed in 105 countries, most notably 30M alone in China. Siemens equipment is found all over the world with significant bases in Europe, Asia and South America.


Siemens EWSD relies on magnetic tapes for backup and billing purposes. Since these magnetic tapes are now old and failing, Siemens EWSD Magnetic Tape Emulation is an attractive option for extending the life of this equipment.

The technology of Siemens EWSD is relatively advanced for its generation. Backup and restore operations proceed relatively quickly, typically taking only 50mins for backup of a large exchange. The tape interface is a variant of SCSI with some additions and changes, and it uses a standard 50-pin IDC ribbon cable. Cables runs are fairly long and the DDS's cable checking feature should be used to make sure that the cable is operating within specification.


To get started with DDS Siemens EWSD Magnetic Tape Emulation the process is fairly simple. There is no need to turn off the exchange, install new software or even replace or add any tape interface cards. In fact the DDS provides a plug-and-play solution for EWSD.

It is possible to copy old tape data onto the DDS using the Siemens exchange as the transfer mechanism. This is a fairly fast operation and the DDS allows the installer to set up a 'disaster recovery' restart tape image to use for unexpected exchange restart events. Therefore there is no need to resort to external media even in an unusual situation

For transfer of backups or billing data from the exchange, we recommend the DDS's network features. An easy-to-use GUI application is provided to make this work. Alternatively for larger or more secure installations a fully-automated backup and mediation system is available.

As a backup, SD cards and USB sticks can be used to transfer data. Care should be taken as these media are not as reliable as the DDS's internal RAID+ data storage system.


While the straight-forward nature of DDS's Siemens EWSD Magnetic Tape Emulation solution means that little training is necessary, it is important to take full advantage of the new features available. The DDS is a drop-in replacement for legacy tape drives, but is also provides a number of new features. With appropriate training and planning, these features can significantly cut the running costs of the exchange maintenance operation.

We work closely with our local partner to delivey training appropriate to the needs of the customer. Our experienced engineers are available on-site both during homologation and afterwards in the install phase.


With detailed internal knowledge of the Siemens tape interface and SCSI operation our engineers are well qualified to deal with any questions which may arise during the roll-out phase or afterwards. For billing and mediation, it is not uncommon for new procedures to be required some years after a successful roll-out. Using the DDS's network and data processing features, combined with our engineers' years of experience, we are able to adapt DDS to most site and network requirements.