Siemens EWSD¶
Siemens EWSD (Elektronisches Wählsystem Digital) was a family of digital telephone switch (exchange) which was used by more than 300 telephone operators in more than 100 countries world-wide, serving more than 170 million subscriber lines in 1998.
According to Siemens, there were more than 1600 engineers involved in EWSD software development in Munich alone, creating more than 45 million lines of code.
EWSD was not only used for analog and ISDN telephony, but also as FuVSt (radio exchange) for the German C-Netz analog cellphone system, as well as as MSC (Mobile Switching Centre) for digital GSM cellular networks.
To our knowlege, there is currently no communications museum on the planet that has a working EWSD exchange in their collection. This is hard to believe, given the incredible significance of this equipment for the world-wide telecommunications of the 1980s and 1990s.
EWSDs at private collectors; interconnect to OCTOI¶
Luckily, there are some private collectors trying to fill that gap: Jan Pesak in Brno/CZ has one EWSD in operation, and jolly (long time Osmocom developer) has also managed to document, tear-down, transport and re-build one at his home in 2023. We published a number of timelapse videos of the dis-assembly and re-assembly in this playlist
In November 2023, we established the first SS7/ISUP interconnect between the EWSD in Brno/CZ and our OCTOI community ISDN-over-IP network.
Documentation / Hacks¶
There is tons of original official Siemens documentation for EWSD floating around, as are some training course materials. We'd like to add some additional bits and pieces here, based on our experience.
Furthermore, we'd also like to create a visual documentation with high-res photographs of each and every circuit board type, EPROM images, etc. Stay tuned.
- EWSD Architecture
- EWSD Components
- EWSD BCM
- EWSD CCGB
- EWSD CCGD
- EWSD CDEX
- EWSD CG-MUX
- EWSD CG11A
- EWSD CMYC
- EWSD CMYM
- EWSD COM-SYPC
- EWSD DLUS-30A
- EWSD FHMA
- EWSD FMTU
- EWSD GPN-YC
- EWSD GPN-YD
- EWSD GPN-YE
- EWSD IOC-CPI
- EWSD IOC-SYPC
- EWSD IOP-MB
- EWSD IOP-UNI2
- EWSD IOP-UNI3
- EWSD IOPC
- EWSD IOPTA
- EWSD LAUB
- EWSD LCMM
- EWSD LCUB
- EWSD LISB
- EWSD MD-TOG
- EWSD MDD
- EWSD MDM
- EWSD MH-SIMP
- EWSD MPU-CPI
- EWSD MTI
- EWSD MU-CPI
- EWSD MUX-MA
- EWSD MUXS
- EWSD OCE-N
- EWSD PEX
- EWSD PHMA
- EWSD PIA
- EWSD PMU-SIMP
- EWSD RM-EA
- EWSD SGCB
- EWSD SILT-C
- EWSD SILT-D
- EWSD SIPA
- EWSD SLMD
- EWSD SSM-16B
- EWSD SSM-8B
- EWSD System Panel
- EWSD T-RC
- EWSD TRM-SYPC
- EWSD TSMB
- EWSD TXA-SYPC
- EWSD Hacks
Updated by laforge 6 months ago · 5 revisions