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!
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
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
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.
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.
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.
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
ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.