Aus telephone voltages and frequencies

[StrandElectric]

Anyone here know the Australian standards for

a) DC voltage on a quiescent telephone line.
b) voltage (peak and RMS) and frequency of ring current . Is it a pure sine
wave?
c) are the standards maintained throughout the Aus system, regardless of
the exchange type and manufacture, eg Ericcson AXE etc.?

Many thanks. I have Googled for hours without sucess. There must be an
Australian standard somewhere!

 

[atec77]

Anyone here know the Australian standards for

a) DC voltage on a quiescent telephone line.
b) voltage (peak and RMS) and frequency of ring current . Is it a pure sine
wave?
c) are the standards maintained throughout the Aus system, regardless of
the exchange type and manufacture, eg Ericcson AXE etc.?

Many thanks. I have Googled for hours without sucess. There must be an
Australian standard somewhere!

it's an elv system so 48vdc is usual and about double on a ring
o
you could just drag the scope out and look

 

[gcd]

Hi,
as far as I'm aware there is no standard for the PSTN itself as an entity
only standards for the equipment connected together and the cabling.

in the old days I'd refer you to TPH1292/1053 which indicates ring signal to
be:
Voltage: open cct EMF of 75-100V. rms
Nominal freq : 17-50Hz
Source impedance:500-2000 ohm
Periodicity: 0.4s on, 0.2s off, 0.4s on 2s off. minimum length of ring 0.5s.

A call indicating device shall operate satisfactorily on a minimum of 4mA of
17Hz ring signal, 5mA of 25Hz ring signal and 6mA of 50Hz ring signal.

The DC voltage from public exchanges and PABXs is nominally -50V wrt earth
within the limits of -44V to -56V.

but as that standard is well and truly obsolete try one of those below.

Chers
Greg
---------------------
Standard Telephones: AS/NZS60950, AS/ACIFS002, AS/ACIFS004, AS/ACIFS040

Customer Switching Systems: AS/NZS60950, AS/ACIFS002, AS/ACIFS003,
AS/ACIFS004

Analog Terminal/Telephone Adaptor (ATA): AS/NZS60950, AS/ACIFS002 (FXO)
AS/ACIFS003 (FXS)

AS/CA S003:2010 Requirements for Customer Access Equipment for connection to
a Telecommunications Network

AS/ACIF S004:2008 Voice frequency performance requirements for Customer
Equipment

AS/ACIF S008:2006 Requirements for customer cabling products

AS/ACIF S040:2001 Requirements for general use Customer Equipment for use
with the Standard Telephone Service- Features for special needs of persons
with disabilities

AS/ACIF S041:2009 Requirements for DSL Customer Equipment for connection to
the Public Switched Telephone Network ANSI Standards

ANSI/TIA-968-A-2002 Telephone Terminal Equipment Technical Requirements for
Connection of Terminal Equipment to the Telephone Network

T1.601:1998 ISDN Basic Access Interface for Use on Metallic Loops for
Application at the Network Side of NT, Layer 1 Specification IEC Standard

IEC 60603-7 Ed 3.0 (2008-07) Connectors for electronic equipment - Part 7:
Detail specification for 8-way, unshielded, free and fixed connectors

 

[atec77]

What's the situation regarding grounding of one side of the line, as you
would with a scope not using isolated or differential inputs?

Dunno
I have to trouble with my portable dicksmith cheapy and believe me
it's a cheapy

 

[StrandElectric]

Thank you Greg. Very comprehensive and just what I wanted.

 

[Jasen Betts]

Ring is some AC voltage (60V?) at 16-2/3Hz superimposed on the -48V
off-hook signal.

Some PABXs and similar devices use a trapezoidal waveform instead
linksys VOIP adaptors produce a fairly good approximation of a sine
wave IIRC. the ring frequency may differ with these too.

What's the situation regarding grounding of one side of the line,

Don't, or atleast don't get caught, it may show up as a fault at the
exchange.

as you would with a scope not using isolated or differential inputs?

Best use differential inputs.

 

[Barry]

Anyone here know the Australian standards for

a) DC voltage on a quiescent telephone line.

52.8 v.

b) voltage (peak and RMS) and frequency of ring current . Is it a pure sine
wave?

130 v.

c) are the standards maintained throughout the Aus system, regardless of
the exchange type and manufacture, eg Ericcson AXE etc.?

Many thanks. I have Googled for hours without sucess. There must be an
Australian standard somewhere!

Set by ACMA.

 

[StrandElectric]

Thanks for that, but I've since got the info that the normal nominal line
voltage is 48 volts DC and the ring current is RMS 90 volts at 16.6 Hz, so I
guess your figures must be the maximum allowed?

 

[atec77]

The 90VAC ring superimposed on the 50VDC line gets you about 140V or so
during ringing with whatever voltage the line drops.

which is why on a hot day it zaps ya on a ring when stripping stuff

 

[Barry]

Thanks for that, but I've since got the info that the normal nominal line
voltage is 48 volts DC and the ring current is RMS 90 volts at 16.6 Hz, so I
guess your figures must be the maximum allowed?

I should explain that I worked for Telstra for 23 years as an analog
exchange technician.
For those exchanges the battery backup consisted of the batteries
being 'floated' across the power supply. The batteries were 24 x 2
volt hence a nominal 48 volts, but the power supply was set at 52.8
to maintain the battery charge.
The ring voltage is/was 80 volts AC which when added to the 50 volts
gives 130 volts peak.
Its enough to give a non lethal shock.

 

[StrandElectric]

The 90VAC ring superimposed on the 50VDC line gets you about 140V or so
during ringing with whatever voltage the line drops.

Actually, I don't think superimposing AC on DC produces such a simple
result... Tyically, a bell is connected via a capacitor so would not even
see a DC voltage. Therefore, offset would not enter the picture

 

[Graeme Zimmer]

Actually, I don't think superimposing AC on DC produces such a simple

result...

Anyone who has felt the effects of ring current will strongly disagree...

It's peak voltage which bites humans, zaps insulation, etc, etc,

................. Zim

 

[Jasen Betts]

my figure quoted above are my memory of what I've neasured on a working
phone line his figure are probably more acurate.

Actually, I don't think superimposing AC on DC produces such a simple
result... Tyically, a bell is connected via a capacitor so would not even
see a DC voltage. Therefore, offset would not enter the picture

yeah the DC helps the AC half the time and hinders it half the time.

But the gain in the help half is worth more than the loss in the
hinder halkf.

when computing power you can ad DC and AC RMS voltages for computing
power in a pure resistance

50VDC + 90V RMS AC will deliver the same power into a resistive load as
140V DC or 140V RMS AC.

 

[atec77]

Anyone who has felt the effects of ring current will strongly disagree...

It's peak voltage which bites humans, zaps insulation, etc, etc,

................ Zim

you forgot bloody hurts through sweaty skin

 

[Barry]

The 90VAC ring superimposed on the 50VDC line gets you about 140V or so
during ringing with whatever voltage the line drops.

Its enough to give a decent boot.

 

[Barry]

which is why on a hot day it zaps ya on a ring when stripping stuff

Back EMF will do that too.

 

[atec77]

Back EMF will do that too.

not in the same manner
if you don't know don't bother

 

[Barry]

not in the same manner

Do you know what back EMF is and when and why it occurs?

if you don't know don't bother

Feel free to ask.

That won't work there.
Ask someone you trust.