# Aus telephone voltages and frequencies

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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!

Re: Aus telephone voltages and frequencies

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

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Re: Aus telephone voltages and frequencies

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

Re: Aus telephone voltages and frequencies

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

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Re: Aus telephone voltages and frequencies

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.

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

Best use differential inputs.

--
ɹǝpun uʍop ɯoɹɟ sƃuıʇǝǝɹ⅁

Re: Aus telephone voltages and frequencies
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

Re: Aus telephone voltages and frequencies
Thank you Greg. Very comprehensive and just what I wanted.

Re: Aus telephone voltages and frequencies
on 9/10/2010, StrandElectric supposed :

I think you will find all the Telstra system is the same and described
in another post.

There are all sorts of differences in PABXs from various manufacturers
and although I cannot define them, lots of PABXs will not work with a
TELSTRA hand set.

For instance FAXes will not work on many PABXs so a dedicated line is
required in an office needing a fax, not just an extension on the
office PABX.

--
John G

Re: Aus telephone voltages and frequencies

52.8 v.

130 v.

Set by ACMA.

Re: Aus telephone voltages and frequencies
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?

Re: Aus telephone voltages and frequencies

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

Re: Aus telephone voltages and frequencies

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

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Re: Aus telephone voltages and frequencies

Back EMF will do that too.

Re: Aus telephone voltages and frequencies

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

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Re: Aus telephone voltages and frequencies

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

Feel free to ask.

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

Re: Aus telephone voltages and frequencies

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

Re: Aus telephone voltages and frequencies

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

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

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

Re: Aus telephone voltages and frequencies

you forgot bloody hurts through sweaty skin

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Re: Aus telephone voltages and frequencies

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

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.

--
ɹǝpun uʍop ɯoɹɟ sƃuıʇǝǝɹ⅁

Re: Aus telephone voltages and frequencies

We are talking about LINE voltage here....not voltage through a
capacitor and through a set of bell windings or any other putative
components.