OBi110 and Intercom
ianst:
Hi QB,
Thanks for the response - I've tried googling every combination of intercom/buzzer/line wiring I can think of and still draw a blank.... ???
The issue I've got is if the Obi can deal with a LINE connection that is permanently open but with a third wire for 'buzzer' - ring.
Ian
Shale:
In your test rig, if you press # from the phone, can you talk back and forth?
ianst:
Hi Shale,
Just tried with a regular phone connected to the PHONE port because the intercom handset doesn't have a keypad.
I get a dial tone, then press #, (the LINE port goes into off hook) then cannot hear anything then 2 seconds later it resets back to a dial tone and the LINE LED goes out and comes back on a few seconds later.
The Call history shows a connected call on LINE1 outbound then a disconnection after 2 seconds.
During that 2 seconds the call status shows both phone and line connected.
Ian
ianobi:
Ian,
I fear I may be the bearer of bad news on this topic. Looking at the “home” phone – CT on the diagram, you have a four wire unbalanced telecom circuit – I’m ignoring the gate release for now.
Pin 1: microphone single wire paired with earth return.
Pin 2: receiver single wire paired with earth return.
Pin 3: Common earth or ground (terms depend on where you live!)
Pin 9: 12v a.c. “ringing” which returns via the receiver to earth.
Effectively, this means that the transmitted speech is using pins 1 and 3 as its audio pair and the received speech is using pins 2 and 3 as its audio pair. The ringing comes in on pin 9 and is disconnected when the handset is lifted.
The OBI is looking for a balanced pair for transmitting and receiving speech and receiving ringing. It might just about be able to cope with the low voltages (they are configurable to some extent), but not with the wiring configuration.
There are types of doorphone that can be made to work with an OBi110, but I don’t think that this is one of them. Maybe this company makes some sort of interface unit with a PSTN line – that would work with an OBi110.
ianst:
Hi Ianobi,
Thanks for your detailed response.
I suspected this might be the case :'( -
I must admit I hadn't researched enough the configuration of the Intercom system before getting it just assuming it would be based on a simple PSTN line system which is what left me confused by all the cables! Lesson learnt - must.do.more.research.. ;)
I've emailed the supplier in case they have any suggestions.
On the off chance anyone else can recommend a UK intercom system based on PSTN technology I would be very grateful.
Thanks again for all the fantastic support.
Ian
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