Applicable Products Part number Description
SL500-LTE1 (EU) SL500-LTE1 (EU) Low Power LTE Cat 1 Serial Gateway
SL500-LTEM (GL) SL500-LTEM (GL) Low Power LTE Cat M / NB IoT Serial Gateway
CSD Overview Many aging applications in use today utilise the circuit switched dialing (CSD) service available on older style modems and communication devices. The CSD service allows a device to connect to a remote location using a dial up modem and establish a direct low latency connection to the host.
The benefit of using CSD connections is the simplicity with which the connection can be established and many applications still use dial up services on their equipment to establish an internet connection to their devices. However, this is slowly changing, and much effort is being put in to modernizing the internet connectivity available in remote locations.
On a more modern device supporting 2.5G and EDGE IP data services, the CSD service is being replaced with a PPP dial up adapter on a host PC using a special call id *99***1#' which establishes an IP packet data connection over a dial up adapter.
The CSD service also allows for connections to be made to the device from multiple locations, where the dialling party simply needs to know the devices' data phone number to be able to dial the units directly and establish a connection to the connected equipment.
CSD Connection Speed The downside of CSD data connection services is that the maximum bandwidth available on a 2G connection is limited to 57.6 kbps and in most applications is limited to 9.6 kbps. In today's fast connected world these are very slow speeds and it would take a long time to download even basic information presented with modern systems. The other issue is the cost of downloading large amounts of data. CSD is charged for by the minute and the time taken to download a 1M file is shown in the following table.
Modem Speed Time Taken (min:sec)
9.6 kbps 15:16
14.4 kbps 10:11
28.8 kbps 5:05
33.6 kbps 4:21
56.7 kbps 2:37
So even at the fastest possible speed it would still take nearly 3 minutes to download the file and as this is charged for by the minute this would cost in the region of £0.15-£0.60 depending on the cost of your call charges.
CSD Supported Cellular Technology CSD data services are available on 2G/GSM and 3G/UMTS cellular data carriers. CSD is not supported at all on 4G/LTE due to the digital IP packet based technology used. As a result, any LTE modem which claims support for CSD will automatically fallback to 2G or 3G when establishing a data call. The same is true for analogue voice calls which are also not supported at all on 4G networks. To perform a voice call exclusively on the 4G network it is necessary to use the VoLTE service offered by the IP Multimedia Core Network Subsystem (IMS).
Not all modern modems support IMS and therefore they only support CSD and Voice calls over the 2G and 3G core networks. This means that when the 2G and 3G networks are finally sunset then these modems will stop working for data calls completely and voice calls unless VoLTE is used.
The latest range of Siretta LTE Category 1 and LTE Category 4 modems support IMS over LTE in addition to CSD and Voice over 2G/GSM and 3G/UMTS network technologies. As a result you can be sure when using a Siretta modem you will be able to support all technologies straight out of the box and the services available to you to use will be dictated entirely by your SIM card provider. The details of the SIM services available on 2G (GSM) / 3G (UMTS) / 4G (LTE) and LTE Cat M and LTE Cat NB IoT are described in the following section.
ZETA Model LTE Category
LTE Region UMTS Region GSM Region IMS Support
GPRS Support
CSD Support
SMS Support
ZETA-NLP-LTEM (GL) M/NB GL
GL
Yes
Yes
No
Yes
ZETA-NLP-LTE1 (EU) 1 EU
EU
EU
Yes
Yes
Yes
Yes
ZETA-NSP-LTE1 (EU) 1
EU
EU
EU
Yes
Yes
Yes
Yes
ZETA-NEP-LTEM (GL) M/NB
GL
GL
Yes
Yes
No
Yes
ZETA-NEP-LTE4 (EU)
4
EU
EU
EU
Yes
Yes
Yes
Yes
ZETA-GEP-LTE4 (EU)
4
EU
EU
EU
Yes
Yes
Yes
Yes
ZETA-N-LTE (EU)
4
EU
EU
EU
No
Yes
Yes
Yes
(GL) = Global Region | (EU) = European Region
SIM Configuration To support CSD it is necessary to enable the service with your SIM card provider in a similar way to how you enable SMS, Voice and GPRS data services. Most SIMs come pre-configured allowing Voice SMS and GPRS but you can switch these services on and off as required. CSD is more usually disabled as a service and is usually switched off by default. You will have to request that the CSD service is turned on before starting CSD on your device.
In addition, some SIM providers offer a dedicated data number for CSD and a dedicated voice number for voice but it is also quite normal to have a single number to provide both services. When using a SIM which supports both services over a single number then the type of call being established can be controlled directly by AT commands on the modem and you can specify a voice or data call for the modem.
The following table shows the typical services available for a modern SIM card and what services are generally turned on by default.
Name Description Default Notes
Voice Make and receive calls x Available on 2G/3G only
SMS Short messaging service x Available on 2G/3G only
MMS Multimedia message service Available on 2G/3G only
CSD Circuit switched dialling Available on 2G/3G only
GPRS Send and receive digital data x Available on all technologies
Fixed Private IP Allocated IP fixed on private network Available on all technologies
Fixed Public IP Allocated IP fixed on public network Available to all
IMS VoIP Voice over LTE (VoLTE) x Available on LTE only
IMS SMS SMS over LTE x Available on LTE only
CSD Dial
Europe Stories
05/01/2027
Worlds first 802.15.4ab-UWB chip verified by Calterah and Rohde & Schwarz to be ...
07/10/2026
Dalet, a leading technology and service provider for media-rich organizations, today announced the latest Long-Term Supported (LTS) release of Dalet Flex. Build...
06/09/2026
June 9 2026, 23:00 (PDT) Dolby and MagentaTV Bring Fans Closer to the FIFA Worl...
21/08/2026
Hardware-style timing shifts for software instruments
Following on from the release of Omniclock, Rapid Flow have launched a new sequencer plug-in that can ...
21/08/2026
Highly anticipated synthesizer ships in October 2026
Iceland-based Love Synthesizers have announced that their highly anticipated synthesizer is now availab...
21/08/2026
Masterpiece PBS The Forsytes has expanded its cast as its begins production in ...
21/08/2026
The BBC has unveiled first-look pictures from The Witch Farm, a new ghost story and mystery set in the Welsh countryside, coming soon to BBC iPlayer and BBC One...
21/08/2026
The BBC and BritBox have revealed the first look of Edward Bluemel as Hercule Poirot in the forthcoming six-part series Hercule from Mammoth Screen and Agatha C...
21/08/2026
eds3_5_jq(document).ready(function($) { $(#eds_sliderM519).chameleonSlider_2_1({ content_source:......
21/08/2026
** MEDIA ALERT **
VIZ Media Takes Over Anime NYC with BLEACH, BLACK TORCH, M...
21/08/2026
Tell us a little bit about your job I'm a Marketing Manager and work across a mix of clients and projects. No two days are ever quite the same, which defini...
21/08/2026
Beat The Lotto dives into the plot behind the 1980s National Lottery scandal
24 August 2026 at 9:35pm on RT One and RT Player
Beat The Lotto is the story o...
21/08/2026
The countdown to the most wonderful night of the year has officially begun!
Host Patrick Kielty is gearing up for another unforgettable Late Late Toy Show nig...
21/08/2026
Meet puppet duo Bellie and Whizz, who are about to explore all the big feelings ...
20/08/2026
Set up your own private remote collaboration infrastructure
SoundBridge have recently put together a tutorial video that provides users with a step-by-step ...
20/08/2026
New V-Control Pro features restore basic functionality
Neyrinck's V-Control software has long been keeping older Avid control surfaces compatible with n...
20/08/2026
TV, BritBox and Mammoth Screen have announced that filming is now underway on th...
20/08/2026
Thursday 20 August 2026
Nina Sosanya, Rizzle Kicks, Roman Kemp and Paul Whiteho...
20/08/2026
Wuppertal August 20, 2026
Transformation Church Elevates Production Communicat...
20/08/2026
The music between the notes Coming together In the middle of 2026, as conversations around artificial intelligence continue to raise questions about how musi...
20/08/2026
Arvato Systems Brings Together Digital Transformation Leaders in the Manufacturi...
19/08/2026
Studio owners invited to have their say on rates cuts
The Music Producers Guild (MPG) are inviting UK-based studios to take part in an in-depth survey that ...
19/08/2026
Vintage-inspired desktop interface revealed
Harrison's latest hardware offering sees them head into the world of audio interfaces, delivering a 10-in/12...
19/08/2026
Granular effect remains locked to scale and tempo
Described as your dream granular effect , Minimal Audio's latest creation is capable of turning any s...
19/08/2026
First polyphonic SWAM instrument incoming
Audio Modeling's latest physical-modelling orchestral instrument is just around the corner, and is now availab...
19/08/2026
There's an early Christmas gift for Bookish fans, as UKTV confirms the re-commission of the hit U&alibi drama, created by and starring Mark Gatiss. Viewers ...
19/08/2026
Wednesday 19 August 2026
Sky gives sports fans the chance to watch multiple liv...
19/08/2026
On Saturday September 5 Katie Taylor will step into the ring for the fight of her life against Flora Pili in front of 80,000 fans in Croke Park. A legendary fig...
18/08/2026
Company launch with stereo-imaging tool
Panoramic is the debut release from Panorama Labs, a new company formed by mastering engineer Nicholas Di Lorenzo. C...
18/08/2026
Control software now available for older interfaces
Focusrite have just announced the launch of an update that extends Control 2 software support for their ...
18/08/2026
Tuesday 18 August 2026
Sky Sports and The Fast and the Curious announce new partnership
Sky Sports and The Fast and the Curious have announced a new long-term...
18/08/2026
Wuppertal August 18, 2026
Riedel Brings Professional Live Production Into the Classrooms of ECURiedel Communications today announced that Edith Cowan Universi...
18/08/2026
Apple today announced changes to its business terms for apps in the European Uni...
18/08/2026
THE HEALY RAES: BLOOD, SWEAT & TEARS AIRS WEDNESDAY AUGUST 19 ON RT ONE AT 9:35PM
A new documentary The Healy-Raes: Blood, Sweat & Tears airs on RT One and ...
18/08/2026
Stunning Irish performances at European Athletics and Swimming Championships rea...
18/08/2026
The two-part series begins Sunday 23 August at 6.30pm on RT One and RT Player
...
17/08/2026
New MIDI processor & macro controller revealed
SHIK have announced that they have opened pre-orders for the S32, a standalone MIDI processor and macro contr...
17/08/2026
Cover extended on innovative motorised pot system
Melbourne Instruments have just revealed that the innovative motorised pot system used in their synths and...
17/08/2026
Latest firmware version now available
1010music have just released a free firmware update that brings some nice new features to their renowned Bluebox digit...
17/08/2026
Rohde & Schwarz showcases integrated defense and test solutions at DALO Industry...
17/08/2026
Calrec's ImPulseV Virtualised Audio Mixing Engine joins NEP Platform, the industry's largest ecosystem of trusted production software, bringing scalable...
17/08/2026
Visitors to IBC 2026 will see how FilmLight is reshaping the modern post pipelin...
17/08/2026
Visitors to Stand 1.C41 can explore innovations in areas such as addressable advertising, hybrid distribution, managed services and operational simplification.
...
16/08/2026
Virtual drummer joins line-up
The latest release from Gospel Musicians adds a virtual drummer to the company's line-up, combining a pair of meticulously...
15/08/2026
In-ear monitoring line-up gains new universal models
In-ear monitoring experts JH Audio have just announced a significant expansion of their Universal-Fit r...
14/08/2026
Latest instalment delivers disco-inspired grooves
The latest addition to UJAM's virtual drum line-up has been designed with contemporary pop, disco, dan...
14/08/2026
Elite range gains giant 24-inch powered sub
The latest expansion of Yorkville's Elite range introduces what the company say is the world's first act...
14/08/2026
Friday 14 August 2026
Breaking news! Sky releases trailer for The Paper, return...
14/08/2026
It's been one year since our client, Cotswolds Designer Outlet, opened its doors and we've loved seeing the scheme come to life. Together, we've hel...
Applicable Products Part number Description 
