Category Archives: GSM Blog

Investigating GSM networks available to us using a CLX SIM

In the article we look at which GSM masts are available to us at our location and see which network will give us the best performance. We also look into establishing a data connection using the CLX SIM card and find the location of our PCB using QUECELL locate system.

We had a board hooked up with 2-way comms to a PC whilst developing the speech storage and playback function on our GSM Alarm Speech Dialler ADs (available at http://www.adventcontrols.co.uk).  We took this opportunity to investigate the network infrastructure we are able to acquire here in our office

GSM Dialler

GSM Speech Dialler with PC connection

Firstly, we send the command AT+CREG? which shows us that the modem is connected and roaming.  We are roaming as we are using the CLX SIM which has access to any GSM network in the UK.

AT+CREG?

+CREG: 0,5

 

Next, we send the AT+QOPS? command to get a list of masts the M66 is able to acquire:

AT+QOPS?

+QOPS: 1,”Vodafone”,”Voda UK”,”23415″

1,0062,305E,1A,22,94

+QOPS: 2,”O2″,”O2 -UK”,”23410″

1,53AC,9BDA,27,23,111       (n.b. 9BDA in hex is 39898 in decimal)

+QOPS: 1,”T-Mobile”,”EE”,”23430″

1,090A,9C47,1F,16,664

 

QOPS: 2 shows us we are currently using the O2-UK mast with location code 53AC and CellID 9BDA.  We can also see masts from T-Mobile (part of EE) and Vodafone are available to us (QOPS:1).  With the CellID we can find the mast we are using on a map

 

O2 Mast

GSM Mast Location

 

Earlier we were using an EE SIM, and this forced us to use a mast in the local retail park which is much further away and out of the screenshot above. This resulted in a signal strength of 16 as opposed to 23 from O2. This is the advantage of using the CLX SIM; it allows the modem to choose the most reliable network.

 

Another advantage of using the CLX SIM is that the GSM device will come with the APN set up correctly by default.  The Access Point Name (APN) tells the network which server your equipment can use. Networks will have different APN for different customers like PAYG or contract.  If you select the wrong one you will have no data access. This is the main cause of issues when using our software and emails. Our boards come with the APN settings for CLX pre-programmed which can be used globally.

 

To demonstrate data connectivity with the CLX SIM cards we will make use of Quectel’s Cellular Positioning System.  This will give is the geographic co-ordinates of the PCB even when indoors.  The modem connects, through the internet, to Quectel’s database of GSM masts and then compares the signal strength from each mast to locate the device.

 

Firstly we must tell the modem the APN which will give us access to the internet as follows:

 

at+qicsgp=1,”connect”,””,””                   …the CLX APN is “connect” with no username or password

at+qcellloc=1                                                     …enquire about our current location

+QCELLLOC: -2.861663,53.353088

 

The at+qcellloc command returns our co-ordinates which we can then paste into Google Maps

QUECLOCATE

Using Cellular Location

The position given by the Quec Locate server is about 0.5 miles out with our high gain antenna.  This is towards a worst case scenario situation given that our PCB is buried deep within a building.  If it were outside it would be much more accurate.

We tried again using the internal adhesive antenna we use for our Gold:Mini Intercom and this time the error was about 0.8 miles.  This is because the internal antenna is optimised for 1800MHz masts which are predominantly located in this direction.

+QCELLLOC: -2.863965,53.361809

GSM ALARM LOCATOR

Low gain antenna location attempt

 

To view our GSM products and for live demonstrations please visit our stand at IFSEC 2018.  We look forward to meeting you.

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Should I buy a 3G intercom or alarm dialler?

We get asked a lot when the 2G network will be shutdown. In Europe, on the whole, nobody really knows yet.  The general consensus is that the 3G network will be shutdown first around 2020 and 2G as late as 2025.  In some countries 2G is no longer in operation (USA, Australia, Japan, Singapore…) but this is not the case in Europe.

Vodafone-will-not-switch-off-2G-until-2025

old phone

2G Phone

4G is obviously great for data but until recently many phone masts did not support audio on 4G/Long Term Evolution (LTE).  Audio on 4G uses a system developed by Qualcomm known as VoLTE.  Originally 4G was data only and your phone switches to 2G or 3G for calls.  Audio on 4G is really only being implemented now by most networks.

https://www.4g.co.uk/what-is-volte/

So, that leaves 2G and 3G for handling calls.  3G uses 2100MHz in Europe.  In general a higher frequency will result in a shorter range.  Also, on the higher frequency bands, your phone is limited by the amount of power it can transmit to 1W.  For comparison, on 900MHz 2G your phone can transmit 2W of power giving a better range.  The lower frequency of 2G and 4G bands will also penetrate walls better than the higher frequency 3G band.  3G also only has one frequency band allocated to it whereas 2G has two.

Europe-could-go-alone-in-waving-goodbye-to-3g-first

3G phone

Early 3G phone

3G therefore doesn’t really offer anything anymore.  It is slower than 4G for data and the coverage is usually worse than 2G which is why the network space is better allocated to 4G, 4G NB and 5G.

So, should you buy a 3G intercom or dialler?  We were developing 3G products but decided to stop simply due to their limited life-span.  They will work on 2G when 3G is shutdown but why pay the extra for a 3G unit?  There is one reason; in the UK the 3 network only offer 3G & 4G so you can only use a 3G unit on this network.  They may continue 3G beyond 2020 for this reason.  Also you may find you have no coverage in your area on 2G but there is coverage on 3G.  This would of course be a temporary solution for you!

3G Alarm Dialler PCB

3G Alarm Dialler

We gave up on 3G and I would not recommend paying extra for a 3G unit.  We are developing 4G products but these have many extra complications with VoLTE and network specific frequency bands so our 4G units are taking some time to develop – but 4G is the future!  We expect to be first with our 4G diallers and intercoms in Europe.

VoLTE Intercom

4G VoLTE Intercom

For further reading please see:

https://www.mobileworldlive.com/featured-content/top-three/operators-vendors-forecast-long-life-2g/

 

Honeywell Accenta/Optima GSM Dialler SMS Sender – Set and Unset Alarm Remotely

Our C4 for Honeywell Accenta & Optima alarms allows you to remotely set and unset your alarm from anywhere in the world.  It will dial, text and email you when the alarm is triggered and armed and disarmed.

D4.01 GSM Dialer with SMS Voltage and Battery Monitoring Testing Video

Just a little video showing some testing being performed on the new D4.01 PCB.  This will be available on the website shortly.

The PCB has two analogue terminals for voltage measurement which can be sent by SMS or by email.  The supply voltage is also monitored for 12V battery operation.
It also has four high/low digital inputs and one volt-free relay output which can be operated by SMS or call.

Citadel Xr2 GSM Alarm Dialer/SMS Sender Wiring Guide Aico Smoke Alarm

We received this question via email:

Hi,

I would like to connect two devices to the Dialer:

Input One : Burglar Alarm

Input Two: Smoke Alarm

I have an Citadel Xr2 alarm system which I assume is pretty standard to get a signal from it [it is!].
The smoke detectors are from the Aico range, and would be interfaced through a Relay base Ei128RBU.

Cheers

Wiring the Citadel Alarm and Aico Smoke alarms to the Advent Controls GSM Alarm Auto-dialer and SMS Sender is very straight forward and the default input settings can be used.  The 0v terminal on the alarm panel and the GND terminal on the dialer must be connected together.  The bell -ve terminal is also connected to the selected input on the dialer.

Citadel Xr2 GSM dialer wiring with Aico Alarm

Citadel Xr2 Wiring Guide

The Aico Alarm has a set of relay output contacts which can be connected directly to Input B (in general ensure they are Volt-free and do not supply mains voltages!!).  Use the COM and NO terminals on the alarm as shown in the diagram.

For a basic setup you will need to send these messages:

master <your mobile number>.   (this sets your phone up as an administrator – remove red jumper afterwards)

callnum <1st number to be rung>.

callnum <2nd number to be rung>.  (you can keep doing this!)

textnum <text recipient>.

textnum <another SMS recipient>.  (again there is space for over 250 numbers)

If you would like the messages to say something specific you can send (for example):

customa the burglar alarm is sounding.

customb the fire alarm is sounding.

If you would like to know when the alarms have stopped sounding send these commands:

inlevela both

inlevelb both

customah the burglar alarm has stopped sounding.

custombh the fire alarm has stopped sounding.

The Advent Controls GSM Alarm dialer and SMS sender is available from the Advent Controls website here.

PAYG SIM Card Deactivation

When using Pay As You Go (PAYG) SIM cards in equipment such as dialers and gate openers you should be aware that the network may chose to deactivate your SIM card should you not meet the minimum usage requirements.  In the UK the strictest networks require at least a call or text message to be sent once per quarter – Lebara Mobile require 1 call/SMS per 3 28 day calendar months.

For details of the terms and conditions for each network I recommend following this link with an excellent article written on the subject:

http://kenstechtips.com/index.php/payg-inactivity-account-termination-and-credit-expiry

Further details can be found here on the basis for these policies:

https://community.giffgaff.com/t5/Blog/Recycling-mobile-numbers-giffgaff/ba-p/8211666

Our GSM equipment has two SIM card Keep Alive functions which automatically send an SMS or dial a number to keep your SIM card within the terms and conditions of the network.  All products have the Keep Alive Text feature which sends an automated SMS message at user specified intervals to their chosen number.  This is set up as follows:

KAT 07000000000,28.       Sends a keep alive message every 28 days to 07000000000

Dialers and Gate Openers with firmware version 3.18 or later additionally have the ability to dial numbers where a voice call is a requirement.  This is set up using the following command:

KAC 01512834306,80.      Dials 01512834306 every 80 days

Should the call go unanswered it unit will retry 4 times and will then send an SMS to the first master number with the following text ‘KAC@Fail’.  In this case a manual call should be made with the following command:

Dial 01512834306.     …or the number of your choice

Where your network requires a call to be made but your device has firmware prior to F3.18 we recommend setting the Keep Alive Text message to remind you to make a manual call for your required interval using the dial command.  Ensure the call is answered.