Intercom system

[Isetech]

A DIY project, or not.

2 days later, the most expensive intercom I have ever installed and it is still not working : ( . Lets see how long it takes for the supplier to figure out why a brand new system, replaced with another brand new intercom out the box, still doesnt work.

I am busy doing some work for a customer, a bit of electrical work around the house, a CCTV installation and a simple intercom replacement.

The intercom installed was a home improvement shop special, I thought I would "upgrade" to a Commax intercom, looking at the supplier who also sells paradox alarm systems (a good brand) you would think Commax is a good brand.

the instruction manual indicates the cables must not be longer than 50 unit to unit and not more than 30 m to the gate unit. the cables on site are at the limit.

Lets hear your thoughts why a simple 1 to 2 unit will not work. This is what I have tried:

Replaced the entire system, with a brand new replacement.

Replaced all the cables with new multi cord cables and then replaced with solid core pure copper coms cables.

Tried cat 5 cable, also no luck.

Removed the the entire system including the cables and returned to the technician at the place I purchased the system, they couldnt tell me why it is not working, it is now sitting with suppliers technician and also cant figue out why the system will not work, he tried replacing the individual units and still no luck.

I think I should just go buy a new home improvement store special at least we know it woks on the site

What a waste of time.

[Justloadit]

Test the unit on your table with a few meters of cable, then increase length

[Isetech]

Test the unit on your table with a few meters of cable, then increase length

That is what we did and even tried a cat 5 pure copper cable ( this by the way is the reason it is important to be aware of what your installer is fitting on your property) to reduce volt drop and the resistance.

I have left it with the supplier to sort out, too much time wasted already.

If they cant get it to work I am going to fit a GSM unit at the gate, a little more expensive, but considering the time wasted already, I could have fitted 3 GSM units with change

[Justloadit]

Seems that there is something wrong with the unit, and not so much the cabling used.
Volt drops at this level are negligible. A typical telephone line can be several kilometers, but the carrier signal is 9V, and the audio is modulated on this DC voltage. So a volt drop does not affect the modulated audio signal.
What can affect the audio signal is the capacitance of the line, which acts as a low pass filter, and attenuated the audio signal which is a few kilohertz.

[Isetech]

It been 2 days and the commax technical department cant figure it out yet.

I thinking the time wasted, its better to scrap the idea and fit the GSM maodule, double the price but half the frustration.

As I have said on many occasions, I am only as good as my supplier technical support. It doesnt pay me to buy product that have crap technical support.

It is clear that Commax support is not very good, a silly problem like this should have bee sorted out in a couple minutes not days.

[Isetech]

Lets have a look at what we have learnt, dont use a Commax intercom if the wire is longer than 5 metres . I can design, wire and program a fully automated PLC controlled system faster than I can install a Commax 1-2 intercom system. that is just sad, rather call the experts .

I am one of those people who wont let this go until I figure out why I cant get what I would have thought was a brain dead DIY project. Which has ended up costing more than the top top of the range GSM module, I know I should just walk away or spend the R 5000 and buy a proper system.

Everyone said a solid comms cable would do the job, it is better to use a solid core over a multi core. A comms cable is 0.2 mm squared.

Call: high 400 mW and 100 mW on low.

Talk is 70 mW

Max cable length :

30m master gate to master - 0.65 , not sure if its metric or imperial.

50m gate to slave (the unit with the power cable) - 0.65 thickness of the wire. If this (0.65) is mm square then everyone selling you the incorrect comms cable (0.2mm)

I need to find out what the each terminal is used for

123456

1234 must be used for the master and slave and 56 for the gate station.

We have a unit at the gate which has a button which calls both master and slave and you can talk to either.

You have a button on the mater and slave to call the other unit and you can talk to each other.

Lets say I run a 0.2 mm square cable from the master to the slave 50 m long, if I twist all the wires together what will the resistance for each core be roughly?

IF we do the same for the other wire 30 mm long?

If the unit draws 400 mW when you press the button, anyone know what the voltage used to sound the buzzer?

If you press the button and talk from master to slave, the sound quality is good. If you talk between the gate and master or slave the quality is good.

It is just the buzzer that sounds really bad when you press the gate button, like the resistance is way to high or the volt drop is too much.

[Isetech]

Now that we have identified a problem and the cable route is longer than your average 5 m installation , a few other things need to be considered. It like a DIY socket outlet installation, any fool can install or replace a socket outlet. However when you start installing sockets outside or in a classified area or a long run which includes various cable supports or ducts in different environment then a quick DIY job might not be that simple.

Considerations:

Cable thickness tinned or solid copper.

Cable design, twisted or parallel, number of twists per meter.

Maybe just a bad batch or design?

[Isetech]

Another consideration is the location of the master and slave.

First you have to understand which is the master and which is the slave.

The slave would be the one with the power cable (with 5 terminals)

The mater the one with 6 terminals.

The master would be located in the middle between the gate and the slave, not the slave in the middle and the master at the far end as indicated by one of the technical staff I spoke to.

[Isetech]

Lastly and I believe this could be the problem, the transformer powering the system is not up to standard or maybe too small or an inferior products (copper etc) are used to cut costs, which explains why it works on a 5 m long wire but not 50 m long cable.