
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
Most recent headlines
05/01/2027
Worlds first 802.15.4ab-UWB chip verified by Calterah and Rohde & Schwarz to be ...
01/06/2026
January 6 2026, 05:30 (PST) Dolby Sets the New Standard for Premium Entertainment at CES 2026
Throughout the week, Dolby brings to life the latest innovatio...
02/05/2026
Dalet, a leading technology and service provider for media-rich organizations, t...
01/05/2026
January 5 2026, 18:30 (PST) NBCUniversal's Peacock to Be First Streamer to ...
01/04/2026
Victoria Mon t Brings the Multi-Hyphenate Mindset to Career Jam 2026 The Grammy-winning singer, songwriter, and producer shared how versatility and self-inves...
01/04/2026
January 4 2026, 18:00 (PST) DOLBY AND DOUYIN EMPOWER THE NEXT GENERATON OF CREATORS WITH DOLBY VISION
Douyin Users Can Now Create And Share Videos With Stun...
31/03/2026
MeyerPro delivered the LED production for the Microsoft Ignite 2025 keynote at Chase Center in San Francisco, using more than 2,700 ROE Visual panels across mul...
31/03/2026
The Media Coding Industry Forum (MC-IF) is expanding membership outreach in 2026...
31/03/2026
ViewLift and MyOutdoorTV (MOTV) have announced the launch of ViewLift Conversational AI Search on the MyOutdoorTV platform. The feature enables natural language...
31/03/2026
The Atlanta Braves and Gray Media have announced a multi-year agreement to simul...
31/03/2026
Gravity Media has delivered broadcast services for TAB Golden Slipper Day at Rosehill Gardens on March 21 and will now cover The Star Championships at Royal Ran...
31/03/2026
Synamedia has announced that Mileto Tecnologia, a Brazilian pay-TV operator, has selected the Synamedia Go platform for its OTT expansion. Mileto is also deploy...
31/03/2026
KMH Integration will attend NAB Show in Las Vegas with a focus on what the company calls AV Casting - an approach built on the idea that professional AV and bro...
31/03/2026
Prime Video will carry live coverage of the first and second rounds of the 2026 Masters Tournament, beginning at 1:00 p.m. ET on Thursday, April 9 and Friday, A...
31/03/2026
The NHL and its U.S. and Canadian broadcast partners have announced a collaborat...
31/03/2026
Daktronics has partnered with Wake Forest to manufacture and install a new end z...
31/03/2026
The National Football League has announced that Las Vegas will host Super Bowl LXIII in 2029 at Allegiant Stadium. The announcement was made at the NFL Annual M...
31/03/2026
The NFL has announced a partnership with TMRW Sports to develop and operate a professional flag football league for women and men. The league will launch with i...
31/03/2026
Sennheiser's Spectera wideband bidirectional wireless system was used by bot...
31/03/2026
Sports Studio Inc., the company behind Free Live Sports, has announced the formation of an Advisory Board with five media and technology executives.
Each of o...
31/03/2026
PSSI and Appear have announced a new phase in their collaboration, with PSSI deploying Appear's X Platform to upgrade its mobile fleet and PSSI Internationa...
31/03/2026
As sports media organization continue to seek out new ways to streamline their p...
31/03/2026
With two new expansion teams and viewership/attendance on the rise, the league's production/broadcast arm and its partner NEP Connected Solutions are busier...
31/03/2026
Spotify has evolved from a streaming platform to an interactive, multiformat eco...
31/03/2026
Lastest New Universal Synthesizer System module announced
Make Noise Music have recently announced the launch of the latest addition to their New Universal ...
31/03/2026
True Stereo DynIR Engine, Virtual Load Shaper & more
Two notes Audio Engineering's Captor X reactive load box and cabinet simulator has built up a solid...
31/03/2026
By Kiera Williams
Every year, a new group of emerging media and entertainment professionals steps into the HPA community - curious, talented, and ready to grow...
31/03/2026
MELBOURNE, Fla., March 31, 2026 - L3Harris Technologies (NYSE: LHX) will release its first quarter 2026 financial results before the market opens on Thursday, A...
31/03/2026
Photo courtesy of NASA. An illustration shows NASA's Perseverance rover operating on the surface of Mars....
31/03/2026
L3Harris Technologies and Comtech Telecommunications Corp. have collaborated to introduce the next evolution in resilient multi-orbit capability for today's...
31/03/2026
Rebel Sport leads ad investment as brands compete for a large, active and qualit...
31/03/2026
Share
Copy link
Facebook
X
Linkedin
Bluesky
Email...
31/03/2026
CueScript, a leading international developer of professional teleprompting solutions, is enhancing its platform with three innovations that elevate flexibility,...
31/03/2026
#GALSNGEAR will host a series of meetups, panel discussions, and networking events during the 2026 NAB Show, taking place April 18 22 in Las Vegas.
The organi...
31/03/2026
At the 2026 NAB Show (April 19-22, Las Vegas Convention Center, Booth #N1328), Imagine Communications is introducing AI assisted scheduling capabilities within ...
31/03/2026
High-density upgrade for mobile fleet and PSSI International Teleport gives PSSI more flexibility for premium live event coverage
PSSI and Appear today announc...
31/03/2026
Solid State Logic Enhances Virtualized System T Platform to Deliver Scalable Clo...
31/03/2026
OWC to Showcase Storage, Workflow Acceleration, and Reliability Solutions for Cr...
31/03/2026
Share
Copy link
Facebook
X
Linkedin
Bluesky
Email...
31/03/2026
OpenDrives, a leader in software-defined video and rich media storage management solutions, will demonstrate several new innovations at the 2026 NAB Show in Apr...
31/03/2026
At the 2026 NAB Show, SDVI will demonstrate how its Rally media supply chain management platform continues to give media operations teams the tools they need to...
31/03/2026
Boland Communications today announced that at the 2026 NAB Show, it will introduce its new QD4K315HDR10, a 31.5-inch QD-OLED monitor delivering exceptional colo...
31/03/2026
Dr. Paul Tapper, CEO of NUGEN Audio, will lead an essential industry discussion at the 2026 NAB Show, examining whether dialog intelligibility is poised to beco...
31/03/2026
BCNEXXT will use NAB 2026 to focus on how broadcasters can turn today's operational and market pressures into opportunity. Meeting with customers in the IAB...
31/03/2026
Mediagenix, a global leader in smart content solutions to profitably connect the right content to the right audience, will showcase its latest innovations at th...
31/03/2026
DHD announces that AI-based audio noise reduction is now available as a powerful new option for its XD3 IP Core. Developed in cooperation with ai-coustics, audi...
31/03/2026
PTZOptics will showcase its vision for intelligent video and advanced camera automation at NAB Show 2026 (#N1902). Through immersive demonstrations and technolo...
31/03/2026
Experience Commerce, a leading full-service digital marketing agency and part of the Cheil SWA Group, has secured the social media mandate for ICONIQA Hotels & ...
31/03/2026
Fabric, the entertainment industry's leader in data and operations solutions, will showcase a major expansion of its media technology platform at NAB 2026, ...
31/03/2026
Share
Copy link
Facebook
X
Linkedin
Bluesky
Email...