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 ...
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...
01/05/2026
January 5 2026, 18:30 (PST) NBCUniversal's Peacock to Be First Streamer to ...
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...
28/01/2026
Music discovery should feel intuitive and personal. That's why we're continuing to give you more control, so you can ask for what you want, shape what y...
28/01/2026
Today, Charlie Hellman, Spotify's Head of Music, shared the following note on the Spotify for Artists blog that the company paid out more than $11 billion t...
28/01/2026
As demand for more complex live sports coverage grows, Balkan broadcast specialist MVP has upgraded its flagship HD1 progressive OB truck with the installation ...
28/01/2026
Luxembourg, January 26, 2026 - SES S.A. ( SES or the Company ), a leading space solutions company, acknowledges the credit rating action announced by Fitch to...
28/01/2026
28 Jan 2026
VEON Notes Kyivstar Group Publication of Selected Full Year 2025 Fi...
28/01/2026
Rohde & Schwarz to host 2026 edition of its online event Demystifying EMC Rohde & Schwarz invites the global EMC community to join a crucial discussion on pre...
28/01/2026
Stadtwerke Wolfhagen Modernize Customer Management with AEP.energysuite from Arv...
27/01/2026
Click for Japanese version
Tokyo, Japan - January 27, 2026 - Akamai Technolo...
27/01/2026
Today, Spotify is proud to support our partner Backline, an industry-leading men...
27/01/2026
With nearly 29 million monthly listeners and clear momentum on Spotify, Net n Ve...
27/01/2026
eds3_5_jq(document).ready(function($) { $(#eds_sliderM519).chameleonSlider_2_1({ content_source:......
27/01/2026
New agreement for uninterrupted UHF connectivity for Australian Defence Force through 2033, With Options Extending to 2041
Luxembourg, January 13, 2026 - Satel...
27/01/2026
Tuesday 27 January 2026
SNL UK creative team expands as Pauli Lovejoy, Annie Ha...
27/01/2026
RT Supporting the Arts is delighted to support a dynamic programme of cultural events taking place across Ireland this February. From visual art, film, music, ...
26/01/2026
Music videos play a huge part in how fans connect with their favorite songs, but...
26/01/2026
Wuppertal January 26, 2026
Riedel and Media Tailor Deliver Unified Broadcast a...
26/01/2026
26 Jan 2026
VEON Unveils the New Beeline Uzbekistan Network Operations Center, ...
26/01/2026
Bookish is created by and stars Mark Gatiss
Images available HERE
Following th...
26/01/2026
Monday 26 January 2026
New Sky Original Series explores Entertainment Juggernaut, The X Factor
Sky today confirmed it has greenlit a premium, definitive docum...
26/01/2026
Monday 26 January 2026
Sky confirms major investment to transform Livingston ca...
26/01/2026
Software for Stable Data Management and Lasting Business Success in Uncertain Ti...
26/01/2026
RT is today publishing a statistical summary of the Register of External Activities for the third quarter of 2025.
The RT Register of External Activities com...
24/01/2026
RT and Virgin Media Television kick off comprehensive free-to-air coverage of t...
23/01/2026
Staines-upon-Thames, UK, 29 July, 2025 - Yospace, the global leader in Dynamic A...
23/01/2026
Spotify's annual Best New Artist celebration honors the rising stars whose talent, creativity, and dedication have propelled them to the music industry'...
23/01/2026
Paramount is transforming its operations by unifying the media supply chains of their top brands into a scalable global pipeline.
This transformation enhances ...
23/01/2026
Every delay costs. When a subtitle fails QC, even the smallest issue can mean missed deadlines, extra vendor costs, or frustrated teams. The new Accurate.Video ...
23/01/2026
Find out where Sare and Suze are now on RT One and RT Player Thursday 29 January at 10.15pm
Hit drama SisterS, created by, written by and starring real-life ...
23/01/2026
Friday 23 January 2026
Sky appoints Lisa Clark as Commissioning Executive for SNL UK
Lisa Clark headshot
PNG (468KB)
Lisa Clark joins Sky as Commissioning E...
23/01/2026
RT is delighted to announce that the RT and F s ireann / Screen Ireland supported short film Retirement Plan has been nominated for Best Animated Short at th...
22/01/2026
Last November, Ed Sheeran returned to his musical roots for an intimate, one-nig...
22/01/2026
Every delay costs. When a subtitle fails QC, even the smallest issue can mean missed deadlines, extra vendor costs, or frustrated teams. The new Accurate.Video ...
22/01/2026
Thursday 29 January 9:35pm on RT 2 and RT Player
The dating show returns with something old, something new and a dater you may already know
Thursday evenings...
22/01/2026
Rohde & Schwarz, Qualcomm, and Motorola demonstrate successful 5G Broadcast comp...
22/01/2026
Dalet, a leading technology and service provider for media-rich organizations, t...
21/01/2026
Wednesday 21 January 2026
Backing Britain on the global stage: Sky becomes an o...
21/01/2026
Fox Corporation Executives to Discuss Second Quarter Fiscal 2026 Financial Resul...
21/01/2026
Baselight v7 brings colourists and post-houses smarter mattes, faster workflows and deeper control
FilmLight, known for its detailed colour toolset and longsta...
21/01/2026
RT News is pleased to announce the appointment of Jackie Fox as its new Washington Correspondent. Jackie is a multimedia journalist with RT News and has repor...
19/01/2026
Monday 19 January 2026
Sky News reinvents News at Ten for the modern audience with The Wrap
Sky News today announces The Wrap, a bold evolution of its 10pm ou...
19/01/2026
DPA Microphones is striking a new chord in piano miking with the debut of its DPK2015 Piano Stereo Kit, an out-of-the-box, plug-and-play miking solution that ta...
19/01/2026
DPA Microphones will present its 4099 CORE Instrument Microphone and redesigned...
19/01/2026
Trianel relies on Arvato Systems for future-proof data center operations
Moving to the cloud: Arvato Systems implements extensive IT migration project
Migrat...
19/01/2026
Celebrating 21 Years of the RT Choice Music Prize
RT Choice Music Prize
In association with IMRO and IRMA
Irish Album of the Year 2025 - Shortlist Announce...
18/01/2026
January 18 2026, 21:30 (PST) Dolby Cinema Arrives in Bengaluru: Dolby Laborator...
Applicable Products Part number Description 
