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.


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.

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.


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:



Gold Mini GSM Intercom: production, testing, inspection

Finally we saw our new Mini Intercom enter production.  It uses a new and novel manufacturing technique which required several iterations to get right.  The end result is a solid, strong lump of fiber glass with a pretty black and gold finish – and yes that’s real gold!  At just 4mm thick this intercom has the appearance of a flush mounted unit but is in fact surface mounted; a common trait for all our Gold intercoms.

4mm thick intercom

Side view

The intercom is fully waterproof. We use the gold finish as it is non-corrosive.  The three parts of the intercom are brazed together forming a water tight seal around the unit rather like a copper pipe is soldered to form a seal.

soldering joint x-ray

Solder seal x-ray

After the soldering process we inspect the intercom using an x-ray to ensure the seal has been formed around the entire perimeter of the unit.

QFN x-ray

Processor soldering inspection

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.

New Firmware Testing

Firmware debugging

v6 Firmware Testing

We’re currently testing the new v6 firmware which offers email support along with:

DTMF tones during calls
Event Logging
Daily health check connection to our server
Email support
Email of balance
Reset logs for monitor errors
Compressed firmware allowing new features
Can include the analogue voltages on customised messages
Event Scheduling (Relay On/Off)
On-board RTC

All looking good for shipping w/c 27/02/17!

Gold Mini Intercom Sneak Preview

I thought I’d share this even though it’s not ready to order yet.  We have a new intercom measuring 10cm x 8cm x 0.5cm.  It actually can be 4mm thick but the rear seal adds 1mm for external applications.  This also makes the audio a little nicer.  We screwed it to a white box for the photo!

GSM Door Phone Intercom

GSM Door Phone Intercom

Due to be available mid-January 2017

C4 GSM Gate and Roller Shutter Control PCB Wiring

C4 Mobile Phone Shutter Controller

The shutter can be opened and closed by calling the SIM card number or sending a SMS text to the SIM card number.  The setup and wiring depends on the configuration of your shutter control panel.

Gate or Garage Door with one ‘Open’ terminal

GSM Roller Shutter Controller

Simple Open Input Controller

For gates and garage door openers with just one ‘open’ connection just the # terminals are used.  Connections are made from the COM# terminal and NO~ terminal.

The following commands are used (sent in a SMS to the SIM card number):

Master <your number>.           …sets your phone up as with admin rights

Add <number>.                       …adds more numbers to the system

Open                                       …open and closes the gate/door

Latch                                       …holds the door/gate open until ‘OPEN’ or ‘OFF#’ sent


Gate or Garage Door with Open and Close Terminals

Phone SMS controller gate roller shutter

C4 to Controller with both Open and Close Terminals

For gates, roller shutters and garage doors with an open and a close terminal the second relay is used.  This allows the GSM unit to close the entry also.


The following commands are used (sent in a SMS to the SIM card number):

Master <your number>.           …sets your phone up as with admin rights

Add <number>.                       …adds more numbers to the system

Channel alt                             …allows first call to open shutter, second call to close it

Open                                       …opens the gate/door

Close                                       …closes the gate/door


Rlymode ring                           …activates output relays whilst phone is ringing

Rlytime xxx.                              …sets the relay output pulse time to xxx seconds


Open/Close send give a pulsed relay output set by the RLYTIME command.  ON*/OFF* and ON#/OFF# activate and deactivate the relay permanently.  Calling the device will operate the relay set by the CHANNEL command (default is #).  CHANNEL ALT will allow one call to operate the # relay and the next to operate the * relay – usefull for opening and closing the shutter.  To operate the shutter only whilst the phone is ringing the RLYMODE RING command is sent.  RLYMODE PULSE return this to the default pulse setting.

The C4 Gate and Rolller Shutter GSM Phone Control PCB is available on our website on the following link C4 Mobile Phone Shutter Controller