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 ...
04/08/2026
Dalet, a leading technology and service provider for media-rich organizations, t...
04/07/2026
April 7 2026, 19:00 (PDT) Detective Conan: Fallen Angel of the Highway Opens in...
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...
17/05/2026
Delta Goodrem's Eurovision Eclipse marks end of a stellar run
17 May, 2026
Media releases
Bulgaria wins Eurovision 2026
Relive every spellbinding mome...
16/05/2026
Helps to deliver a clean, balanced midrange
Developed alongside Newfangled Audio, the latest plug-in in Eventide's software collection has been designed...
16/05/2026
Brings onboard stem rendering to RANE System One
Engine DJ have just released Engine DJ 5.0, a free update for their Engine DJ OS embedded hardware and Engi...
16/05/2026
Boris FX Continuum Pairs AI Precision and Advanced Creative Controls
Jessie Electa Petrov May 16, 2026
0 Comments
The 2026.5 release adds automatic de...
16/05/2026
Share
Copy link
Facebook
X
Linkedin
Bluesky
Email...
16/05/2026
Share
Copy link
Facebook
X
Linkedin
Bluesky
Email...
16/05/2026
Share
Copy link
Facebook
X
Linkedin
Bluesky
Email...
16/05/2026
Share
Copy link
Facebook
X
Linkedin
Bluesky
Email...
15/05/2026
Seattle Sounders FC and Seattle Reign FC, in partnership with RAVE Foundation an...
15/05/2026
Dan Brumm has served as sound designer on Bluey, the Australian children's t...
15/05/2026
The Professional Audio Manufacturers Alliance (PAMA) and Shure Incorporated are accepting applications for the 6th annual Mark Brunner Professional Audio Schola...
15/05/2026
Netflix has announced an expanded NFL schedule for 2026 and beyond under a four-year partnership extension with the NFL through the 2029-30 season. Each season,...
15/05/2026
Ateme is supporting TVRI (Televisi Republik Indonesia) with a contribution and d...
15/05/2026
Concacaf has announced the launch of a new website and mobile app built on Deltatre's FORGE platform. Concacaf.com and the mobile app, available on iOS and ...
15/05/2026
Eutelsat has announced the launch of QBC Business Economic Channel by Qatar Media Corporation, broadcasting in 4K/UHD via Eutelsat's 7/8 West video neighbo...
15/05/2026
Major League Soccer has announced four original content series timed to the 2026...
15/05/2026
The Alliance for IP Media Solutions (AIMS) has announced it will exhibit and present at InfoComm 2026, taking place June 13-19 at the Las Vegas Convention Cente...
15/05/2026
InfoComm 2026 will take place June 13-19 (exhibits June 17-19) at the Las Vegas Convention Center. The show will include sessions and exhibits covering broadcas...
15/05/2026
Tracy McGrady's Ones Basketball League (OBL) and FuboTV Inc. have announced ...
15/05/2026
Disguise has partnered with Creative Technology (CT) to deliver visual playback ...
15/05/2026
Sony Electronics has announced two new products for professional imaging: the Alpha 7R VI full-frame mirrorless camera and the FE 100-400mm F4.5 GM OSS super-te...
15/05/2026
In-venue and creative video staffers at the professional and collegiate level ha...
15/05/2026
Ratings Roundup is a rundown of recent rating news and is derived from press rel...
15/05/2026
For sports organizations, the most valuable assets are often the most sensitive:...
15/05/2026
The NFL's broadcast partners released their 2026 regular season schedules ye...
15/05/2026
When MMA icons Ronda Rousey and Gina Carano meet inside the Hexagon at Intuit Do...
15/05/2026
Daniel Roher attends the Tuner Premiere during the 2026 Sundance Film Festival at Eccles Theatre on January 22, 2026 in Park City, Utah. (Photo by Neilson Bar...
15/05/2026
Last night, the Spotify Podcast Awards in Mexico returned to the country's capital. Now in its second year, the evening honors creators whose voices are hel...
15/05/2026
Rebranded show announced
Ahead of their 2026 return, Music Expo have announced that they have now officially changed their name to the MONO Music Conference...
15/05/2026
Fuzz pedal joins UK companys line-up
UK-based pedal makers Buzzing Bugs Audio Devices have recently unveiled their latest creation, the Bolster. Said to pay...
15/05/2026
Joint Statement: News Bargaining Incentive
28 April, 2026
Media releases
The vibrancy of Australian democracy relies on the robust and open exchange of new...
15/05/2026
Call it Deltavision, Australia's through to the Grand Final of this year'...
15/05/2026
Join Calrec at MPTS 2026 | May 13-14 | Stand A40 | Olympia, London We're looking forward to meeting up with customers and partners at this year's Media ...
15/05/2026
86% of media planners would move more linear TV budget to CTV if they had show-level targeting and reporting - and 65% would also shift dollars from programmati...
15/05/2026
Share
Copy link
Facebook
X
Linkedin
Bluesky
Email...
15/05/2026
Clear-Com will showcase new communications solutions and major platform updates at InfoComm 2026 (Booth N7005), June 17-19, in the North and Central Halls of t...
15/05/2026
Following an outstanding inaugural year in 2025, Rise AV is proud to announce the return of its flagship leadership initiative, Elevate. The programme continues...
15/05/2026
Berklee Announces Lineup for Inaugural AI Music Summit The three-day event puts musicians at the center of the future of music creation, ethics, and the indus...
15/05/2026
Lightware returns to InfoComm 2026 with a focused showcase of scalable USB-C connectivity, next-generation AV-over-IP solutions, and technologies that help over...
15/05/2026
Share
Copy link
Facebook
X
Linkedin
Bluesky
Email...
15/05/2026
Share
Copy link
Facebook
X
Linkedin
Bluesky
Email...
15/05/2026
Share
Copy link
Facebook
X
Linkedin
Bluesky
Email...
15/05/2026
Share
Copy link
Facebook
X
Linkedin
Bluesky
Email...
15/05/2026
Share
Copy link
Facebook
X
Linkedin
Bluesky
Email...
15/05/2026
Delivering a live, arena-scale production of a massively popular band is no small feat. Between expansive in-arena LED walls and a global live stream fed to onl...
Applicable Products Part number Description 
