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
11/12/2025
Dalet, a leading provider of cloud-native, end-to-end media workflow solutions, ...
01/12/2025
01 Dec 2025
Kyivstar and Ukrainian Ministry of Digital Transformation Select Go...
01/12/2025
The prequel to the global hit Sky Original mob crime saga, Gomorrah' is a s...
01/12/2025
Featuring Florence Welch, Red Hot Chilli Peppers' Flea, designer Bella Freud...
01/12/2025
Fox Corporation Chief Financial Officer Steve Tomsic to Participate in Upcoming ...
01/12/2025
Arvato Systems' Virtual Private Cloud (VPC) Receives BSI C5 Certification (T...
01/12/2025
Summary This short video gives you an summary of the changes in under two minutes.
--...
01/12/2025
As the festive season approaches, RT Supporting the Arts is proud to showcase a...
01/12/2025
Festive specials of Christmas in Kilmainham presented by Marty Whelan, High Road Low Road, Callan Kicks the Year and Keys to My Life
Ring in the New Year with ...
01/12/2025
Architect and television presenter Hugh Wallace, best known to RT audiences as a long-serving judge on Home of the Year, has died at the age of 68.
In a state...
28/11/2025
It's easy to ignore those little red update available badges. But when it ...
28/11/2025
Friday 28 November 2025
Sky Sports x Slawn drop limited-edition football jersey...
28/11/2025
Rohde & Schwarz shows resilience in a challenging environment, revenue exceeds t...
28/11/2025
Unwrapped: The Toy Show Appeal - airing this Sunday on RT One and RT Player- s...
27/11/2025
27 Nov 2025
GSMA brings M360 Eurasia 2026 to Samarkand in partnership with VEON...
27/11/2025
Tahar Rahim and Izuka Hoyle star in the gripping six-part Sky Original from Acad...
27/11/2025
Thursday 27 November 2025
Sky Arts Reveals the Nation's Greatest Basslines - and Queen Reign Supreme
The UK's most iconic basslines have been revealed...
27/11/2025
Rating reflects rating progress across areas including policies, diversity & inclusion, health & safety and Net Zero leadership
Winchester, UK, 27 November 202...
27/11/2025
What are the industry standards for Retail Media? Kathryn explains that certification is based on the IAB Europe Retail Media Measurement Standards and the IAB ...
27/11/2025
World champion boxer and Irish sporting icon Katie Taylor will be in studio this...
27/11/2025
Roblox, one of the world's most popular online gaming platforms for primary ...
26/11/2025
Book podcasts are booming. On Spotify, you'll find everything from celebrity book clubs to deep dives with bestselling authors. And in markets where audiobo...
26/11/2025
YouView Achieves Greenly Gold Certification for SustainabilityNov 26, 2025
YouView is proud to announce a Gold Certification award from Greenly for our perform...
25/11/2025
Tracy Bonareri Onchoke, an investigative journalist from Kenya is the winner of the Thomson Foundation's Young Journalist Award 2025.
The 26-year-old-sele...
25/11/2025
The best playlists, podcasts, and audiobooks bring a little extra magic to your daily routine. With new features and offerings, Spotify Premium delivers even mo...
25/11/2025
Comprehensive new research confirms what we already knew: Australian music fans love the quality, quantity, and access they have to new and local music on strea...
25/11/2025
Applicable Products
Objectives The purpose of this application note is to give a brief background on 5G (NR) wireless communication an explain the reason a SN...
25/11/2025
25. November 2025 Cecilia Pierron
Last week, we took part in OnDAM 2025, an educational conference fully dedicated to DAM, hosted by Activo Consulting. The ...
25/11/2025
25 Nov 2025
VEON's QazCode and MeetKai Sign Agreement to Power National LLM...
25/11/2025
UKTV has acquired a high-profile slate of US dramas from Paramount Global Conten...
25/11/2025
A symphony of genius, rivalry and vengeance, boldly reimagined from Peter Shaffe...
25/11/2025
Article courtesy of Cinematography World
Read the article
FilmLight has finalised the prestigious 2025 FilmLight Colour Awards jury and welcomed award-winning...
25/11/2025
Article courtesy of Prensario
Read the article
La serie fue dirigida por Juli n de Tavira, Rodrigo Santos, y David Leche Ruiz, con direcci n de fotograf a a...
25/11/2025
Article courtesy of The Hollywood Reporter
Read the article
The awards, celebr...
25/11/2025
Article courtesy of Televisual
Read the article
Already live in Los Angeles and rolling out in New York and London, Nara gives producers, colourists, conform ...
25/11/2025
Article courtesy of Digital Media World
Read the article
ARTONE post-house in Tokyo is the first facility in Japan to integrate Baselight M, choosing its prec...
25/11/2025
Article courtesy of The Hollywood Reporter
Read the article
Once hidden in post-production suites, the artists who make movies and TV shows look the way they ...
25/11/2025
Article courtesy of Deadline
Read the article
The Brutalist' & Bad Bunny's Nuevayol' Music Video Among 2025 FilmLight Colour Award Winners - Cam...
24/11/2025
Robyn made her long-awaited return to the stage this week, as Spotify and Acne Studios brought friends and top fans together for an unforgettable evening at the...
24/11/2025
After more than two years of redevelopment, FC Barcelona returned to its spiritual home on November 22, hosting Athletic Club in the first La Liga match at the ...
24/11/2025
24 Nov 2025
Kyivstar Launches Starlink Direct to Cell Satellite Connectivity in Ukraine Today's Launch Makes Ukraine the First Country in Europe Where Star...
24/11/2025
Ahead of the new ninth series of Dancing with the Stars, kicking off in January 2026, RT and Shinawil have announced the arrival of three new faces to the hit ...
21/11/2025
Fans have been counting down the days until the final theatrical chapter of Wicked is revealed. To celebrate the highly anticipated release of Wicked: For Good ...
21/11/2025
Last week, Spotify turned up the volume in Seoul with the return of Spotify Hous...
21/11/2025
Wiesbaden, November 21, 2025. The SGL Carbon site in Meitingen has reason to celebrate as one of its trainees received a special award. Elias Stemmer was honore...
21/11/2025
Sky Media's £2m award-winning sustainability initiative crowns its first charity as this year's standout changemakerFriday 21 November 2025
GoodGym nam...
21/11/2025
As COP30 draws to a close, the International Electrotechnical Commission (IEC), ...
20/11/2025
Your playlists are personal. They're the soundtracks to your road trips, your quiet mornings, and your biggest celebrations; collections of memories and dis...
20/11/2025
Spotify, uzun s redir zerine al t T rk m zik k lt r n n ikon haline gelmi ...
Applicable Products Part number Description 
