GSM Intercoms – popular with spiders!

We received an early intercom back in the post today for a firmware update.  The early versions used the # key to release the gate instead of the * key we use now.  For reasons best left to a mathematician to explain decoding the # key is harder than decoding the * key so we swapped over a couple of years ago.

Advent Controls GSM Doorphone

Old GSM Intercom

We decode audio in software using a Discrete Fourier Transform to determine what frequency sounds are present, if any.  Searching for the * key frequencies always works better given the sample rate we use.  It’s a bit too complicated to understand we just know it works better this way.

Spiders webs inside GSM intercom

3 year old GSM Intercom

What is remarkable and not unexpected is how many spiders we found had been living inside the unit.  They’re dead now of course!  We often get asked what the IP rating of the intercom is and people seem disappointed that it is only IP45.  This is due to the cable chute in the rear which is fully open but pointing downwards.  To rain water falling from above we have every interface fully sealed and have never had issues with water ingress – apart from one unit which was missing a seal but we don’t count that!  This unit has been outside for 3 years in all conditions and we’re happy to report the spiders’ home has never been flooded.

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