S2M fail-safe redundancy

 AS551 Master VoIP PRI GSM gateway
The AS551 is a GSM interface (so-called GSM gateway) between fixed and mobile networks by which the communication of a telephone system, can be made directly in the mobile networks independently from the fixed-line network operator. This increases the independency of the communication channels of a company, an authority or other institution in case of line failure and partial line disruptions.
The AS551 VoIP/PRI pass-through* is inserted directly into the PRI trunk line of the PBX. No additional port is required at the PBX. All functions are possible with any telecommunications system that supports S2M services. In case of the communication infrastructure need to be upgraded, e.g. if the existing ISDN30 technology is replaced by VoIP, but the fallback level to the mobile network is mandatory, the AS551 can be reconfigured from S2M connection to VoIP operation mode. In the maximum setup, using an AS551 master with three AS551 slave units up to 30 GSM / UMTS / LTE radio channels in parallel are possible.
*Pass-Through Voice Backup means:
The AS551 detects if the S2M trunk is available or not. In case of a failure or serious errors, all calls are automatically routed via the AS551 mobile radio line. In addition, pass-through can also take over routing functions or perform parallel calls (mobile twinning).
In addition, it is possible to send SMS short messages via SIP message or short message API.
Other additional options such as a SIM card changer or optional features such as: the Telnet controller, the SNMP module. All optional software enhancements can be fully tested with a free 28-day Test-license.
* Pass-Through * is only available on the S2M interface.
Manual - EN
FAQ AS55x - DE

Functional overview

Interfaces- 2,4,or 6 Quad-band radio modules for
EGSM 900/GSM 1800/GSM 1900
- Integrated antenna splitting
- Primary Rate Interface
S2M point-to-point (PRI)
- LAN network 10/100 Base-T
- USB service interface
- Connetions for up to three
AS551 Slave units with each
8 additional radio channels
- Direct call can be defined individually
for each radio channel
- Assignment of the radio channels by groups
- Call back unrestricted, limited by Blacklist,
Whitelist or DTMF code
- Storing answered and unanswered calls
- The link connection to a called mobile
subscriber is stored in the device and
is used for the callback.
- Callback request via SMS short message
- Very fast connection setup PBX
to mobile radio
- Full dial-up capability
- GSM to ISDN/IP number display (CLIP)
- Relocation from mobile to fixed
with GME * (optional)
- SMS short messages via TELNET *
or short news API *
* With a software module (optional)
Overlap dialing-  Limited dial-in by CLIP
Announcements- Operator guidance by various
dial tones, melodies or voice announcements
Individual announcements could be
generated on demand.
- Causes (ISDN causes) are adjustable
- Built-in LCR functions, routing tables
for destination and source call numbers
- Possibility of blocking certain numbers
or prefixes
- Adjustable phone number display
- GSM minimum signal quality
for connection setup
- Direct call per external GSM subscriber
adjustable GSM > ISDN/IP (CLIP) etc.
Maintenance- PC configuration software for Microsoft
Windows© 9x/NT/2000/XP/VISTA/Windows 7,8,10
- Remote configuration and maintenance via LAN
ReverseIP or GSM data channel
- Configuration and maintenance during operation
- Firmware update via LAN or via GSM data channel
- Operating status display via LEDs
- Troubleshooting by local or remote
recording of traces which can be stored in
text or Wireshark© format.
- Monitoring via SNMP *
* With a software module (optional)

Technical data

Radio moduleCinterion MC55i or TC63i
GSM quad-band
Class 4 (2W at 850/900MHz)
Class 1 (1W at 1800/1900MHz)

(optional 3G)
Cinterion/Gemalto EU-3 UMTS or PH8
USB 2.0 Typ B (USB 1.1 kompatibel)
*Driver needs to be installed,
via LAN-network, GSM CD-Data, ReverseIP
ISDN interfacePrimary Rate Interface (PRI)
with DSS1 protocol
S2M (PRI)S0 RJ45 (8pol. Western plug) female
with PassThrough
IP-interfaceRJ 45 Ethernet 10/100 Base-T
ProtocollsSIP 2.0 / UDP as a server,
Client or Peer-To-Peer
Additional protocolls:
Authentification: MD5
CodecG.711 µ-law, G.711 a-law
Interfaces AS55XMaster resp. Slave connector, RJ45
Short message
or API (optional)
AS551 Master:

AS551 Slave:
IP (SIP) - GSM interface
with 6 channels 19" rack (1U/84HP)
Extentions for AS551 Master
with 8 additional GSM channels
19" rack (1U/84HP)
IEC power connector,
integrated power supply
90 - 264 V AC
max. 1,8 A
47 - 440 Hz
Antenna1 Antenna splitter
6 x 1 (Master) for one SMA female
1 Antenna splitter
8 x 1 (Slave) for one SMA female.
Sizeapprox. W 485mm x H 45mm x D 300 mm,
19" rack 1U/84HP (DIN 41494 SC48D)
Weightapprox. 2500 Gramm
Power consumptionAS551 Master:
Stand by typically 90mA
Max. 150mA
equates 21 Watt resp. 35 Watt
(6 radio channels)
Gesprächsbetrieb typisch 150mA
Maximal 225mA
equates 35 Watt resp. 53 Watt
(6 radio channels)

AS551 Slave:
Stand by typically 120mA
Max. 200mA
equates 28 Watt resp. 47 Watt
(8 radio channels)
Gesprächsbetrieb typisch 200mA
Max. 300mA
equates 47 Watt respw. 71 Watt
(8 radio channels)
Work environmentOperating temperature:
5°C to 40°C
Storage temperature:
-10°C to 70°C
0% to 90%
Subject to modifications!