History in Australia
Originally time-clocks were used, however they can easily lose accurate time and are not easily adjusted for daylight saving time. Zellwegers were first introduced in Australia in 1953, however were not compliant with modern harmonic disturbance standards. The second generation was introduced in the 1970s and was more reliable.
A variety of devices can still be seen across Australia.
In at least some parts of Sydney, the ripple frequency is 1050 Hz. The signal usually consists of several bursts of a few seconds on and off, followed by a period of up to 50 seconds on. This is coded to affect only selected equipment. Occurrences are very frequent, sometimes several times an hour throughout the day, not just at evening and morning off-peak times. See example capture:
The bright line at 50 Hz is the power frequency, followed by odd harmonics at 150 Hz, 250 Hz and so on. The ripple being turned on and off is clearly visible at 1050 Hz.
Read more about this topic: Zellweger Off-peak
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