Hi all,
First post for me here, looking for advice.
Please be gentle with me, I need to connect up new replacement mixer amp after our old one blew up through old age last week, as a electrician I can pretty much follow instructions and wire it up. We mainly use the pa for backgound music and more importantly for telephone paging.The old system did not have a dedicated phone in connection the phone system was plugged into mic 1 XLR socket.The new system does have a pair of telehone "in " euro plug connections which are marked as hot & cold. I have made up a short fly lead with a XLR socket to accomadate the XLR plug and I will follow the polarity through to the euro plug tel input as pin 2-hot and pin 3-cold my question is does it matter if hot & cold are reversed ? if so how can I establish which is hot and cold from the telephone system it is not apparent from inspection. I dont want to damage the new amp with a hit & miss approach.
Cheers for any info...Dave
First post for me here, looking for advice.
Please be gentle with me, I need to connect up new replacement mixer amp after our old one blew up through old age last week, as a electrician I can pretty much follow instructions and wire it up. We mainly use the pa for backgound music and more importantly for telephone paging.The old system did not have a dedicated phone in connection the phone system was plugged into mic 1 XLR socket.The new system does have a pair of telehone "in " euro plug connections which are marked as hot & cold. I have made up a short fly lead with a XLR socket to accomadate the XLR plug and I will follow the polarity through to the euro plug tel input as pin 2-hot and pin 3-cold my question is does it matter if hot & cold are reversed ? if so how can I establish which is hot and cold from the telephone system it is not apparent from inspection. I dont want to damage the new amp with a hit & miss approach.
Cheers for any info...Dave
Sorry but don't know what you're talking about 🙁
What is exactly "telephone paging"?
How can you connect a phone (telephone handset?) to an XLR connector and to a Mic input?
They are most incompatible.
Not forgetting that a telephone line carries between 24 and 48 V DC ... plus 60 to 110V AC low frequency ring bell voltages.
Please post a link to your mixer manual, plus brand and model.
What is exactly "telephone paging"?
How can you connect a phone (telephone handset?) to an XLR connector and to a Mic input?
They are most incompatible.
Not forgetting that a telephone line carries between 24 and 48 V DC ... plus 60 to 110V AC low frequency ring bell voltages.
Please post a link to your mixer manual, plus brand and model.
The Hot and Cold from the Source should be isolated from Chassis.
If transformer type output they are also isolated from signal ground.
This type can be wired with Hot an Cold swapped.
Many Sources use the cheaper electronically balanced output stage.
This has a connection from Hot and Cold to Signal Ground.
Check with the manufacturer that the outputs can be swapped into the Receiver unit.
I thin they can be swapped, but not sure.
Pin1 of your XLR at BOTH ends should be connected to CHASSIS, not to Signal Ground.
Look up Jensem/Whitlock and find
Pin1 Testing with the "Hummer"
or find Whitlock's presentation
An Overview of Audio System Grounding & Interfacing
If transformer type output they are also isolated from signal ground.
This type can be wired with Hot an Cold swapped.
Many Sources use the cheaper electronically balanced output stage.
This has a connection from Hot and Cold to Signal Ground.
Check with the manufacturer that the outputs can be swapped into the Receiver unit.
I thin they can be swapped, but not sure.
Pin1 of your XLR at BOTH ends should be connected to CHASSIS, not to Signal Ground.
Look up Jensem/Whitlock and find
Pin1 Testing with the "Hummer"
or find Whitlock's presentation
An Overview of Audio System Grounding & Interfacing
If it is a dedicated telephone input, this input must conform to Bt requirements and will in that case have a 600R isolated impedance that doesn't mind which way around the input is phased.
Thanks for the replies.
The new amp is a Inter-m PMU 120M the very latest network compatable system with bells & whistles http://international.inter-m.net/media/uploads/products/files/PMU_5.pdf
What confused me is why mark something hot/cold if it doesn't matter anyway?
I'm pretty sure that following the old set up that had the exchange "tel out" connected to XLR micc 1 input on pins 2 & 3 if I connect pin 2 to hot and pin 3 to cold on the dedicated "tel in" on the new amp all will be fine...I'll give the phone people a call to verify.
The new amp is a Inter-m PMU 120M the very latest network compatable system with bells & whistles http://international.inter-m.net/media/uploads/products/files/PMU_5.pdf
What confused me is why mark something hot/cold if it doesn't matter anyway?
I'm pretty sure that following the old set up that had the exchange "tel out" connected to XLR micc 1 input on pins 2 & 3 if I connect pin 2 to hot and pin 3 to cold on the dedicated "tel in" on the new amp all will be fine...I'll give the phone people a call to verify.
can't say about european standards but on a 4 pin J11 (standard phone jack) the center pins should be red(+),green(-) the outer pair would be yellow(+) black(-) and with the lock tab facing up and left to right yel,red,grn,blk
flipping the pins won't matter to the audio but if the unit your using has "priority page features" or "mute functions" it could affect these type of functions.
flipping the pins won't matter to the audio but if the unit your using has "priority page features" or "mute functions" it could affect these type of functions.
Agree that a dedicated phone input must match International Standards .
And Hot and Cold labels *may* be there to help an installer who brings audio in through a shielded cable or something, (I would, even if in theory "telephone does not need it") but fact is that they are sometimes switched at random (never understood why) by the Phone Company itself, so the input should better accept it both ways.
I still can't believe (meaning you were very lucky) that earlier you coild hook a Phone line to a Mic input ... and it worked.
I guess it must have been somewhat old equipment with a true transformer balanced input ... and even so.
Phone signal is much louder than typical Lo Z mic one.
Oh well. 😉
And Hot and Cold labels *may* be there to help an installer who brings audio in through a shielded cable or something, (I would, even if in theory "telephone does not need it") but fact is that they are sometimes switched at random (never understood why) by the Phone Company itself, so the input should better accept it both ways.
I still can't believe (meaning you were very lucky) that earlier you coild hook a Phone line to a Mic input ... and it worked.
I guess it must have been somewhat old equipment with a true transformer balanced input ... and even so.
Phone signal is much louder than typical Lo Z mic one.
Oh well. 😉
Tell me about it! 😀
We used to have a leased line for our radio telephone system at work - the transmitter site was high on the hill, and the base station down in the valley - I think the line was about 1 mile? (you were charged - a LOT - by the distance).
Anyway, it worked by sending audio up and down the line (obviously), but also switched between transmit and receive, to do this it simply reversed the DC voltage on the line.
Any time any BT engineers worked anywhere on the length of the line they invariably connected it back the opposite way 😀
As it was a HUGE job trying to get BT to even understand what they had done (never mind getting an engineer out to correct it), we simply used to reverse the connections at our end 😀
Yes your right JM Fahey
"I still can't believe (meaning you were very lucky) that earlier you coild hook a Phone line to a Mic input ... and it worked."
The digital exchange should not have been connected to the micc input in the first place, this was done by the telephone installers who perhaps should have known better. When using the paging feature you had to hold the handset at arms length and even then the sound wasn't very coherant.
I'll hook up the new system tomorrow, the kit arrived on Friday in a re-sealed box with no instructions, untidy mains lead with loose flex tie and dirty fingerprints on the base, seems we have been sent out a second hand unit passed off as new Not very happy...I will be fumming if it's DOA....to be continued>>>
"I still can't believe (meaning you were very lucky) that earlier you coild hook a Phone line to a Mic input ... and it worked."
The digital exchange should not have been connected to the micc input in the first place, this was done by the telephone installers who perhaps should have known better. When using the paging feature you had to hold the handset at arms length and even then the sound wasn't very coherant.
I'll hook up the new system tomorrow, the kit arrived on Friday in a re-sealed box with no instructions, untidy mains lead with loose flex tie and dirty fingerprints on the base, seems we have been sent out a second hand unit passed off as new Not very happy...I will be fumming if it's DOA....to be continued>>>
Well I called the phone people and the best answer was " I don't think it matters" not a definate answer but the best I was going to get. Another issue arose regarding the resistance of the 100v speaker system. I did a check with my meter which gave me a resistance of 11 ohmns. This was somwhat lower than the 83 ohmns allowed by the amp. Which was worrying.
Luckilly It seems that I was using the wrong type of meter.... I should have used a impedance meter rather than a standard multimeter which would give false readings. So as the system had been operating on a old standby amp for a week I had to persume that all was ok with the speakers and I hooked everthing up turned it on and waited with baited breath.......the outcome being that everthing works fine...in fact the telephone paging is much clearer than it was previously.
Job done..thanks for the input guys...
Luckilly It seems that I was using the wrong type of meter.... I should have used a impedance meter rather than a standard multimeter which would give false readings. So as the system had been operating on a old standby amp for a week I had to persume that all was ok with the speakers and I hooked everthing up turned it on and waited with baited breath.......the outcome being that everthing works fine...in fact the telephone paging is much clearer than it was previously.
Job done..thanks for the input guys...
The HOT and COLD are labels for "balanced lines". Hot is (+) and Cold is (-) polarity. And GND is well, ground or chassis.
Pin 1 = Gnd
Pin 2 = Hot
Pin 3 = Cold
If you're connecting an unbalanced source (in this case, your phone), you can connect your source to pins 2 and 3. It doesn't matter which goes which, as if you reverse it, you're just basically doing a "polarity reverse". On the mixer, there is a button for that, and basically that's what it does... flip lines 2 and 3 via relays.
If you use an ordinary multimeter to measure the line impedance it will read very low (as it is only measuring the resistive part of the primary impedance), you need to make such measurements with an instrument that uses AC current to make the measurement if it is to make any sense.
11 ohms would be reasonable for an 100V system when measured at DC, make the measurement at a KHz and it will be much more sensable.
There are trivial bridge mthods you can use if you have a signal generator and a pot of a few hundred ohms, it will only get you |Z| but is simple to set up.
Regards, Dan.
11 ohms would be reasonable for an 100V system when measured at DC, make the measurement at a KHz and it will be much more sensable.
There are trivial bridge mthods you can use if you have a signal generator and a pot of a few hundred ohms, it will only get you |Z| but is simple to set up.
Regards, Dan.
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