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AirAura X1 / Dec 2016
G E N E R A L I N F O R M A T I O N
Analog Phone Lines
Discrete left/right analog “phone line” STL’s are not recommended because of the
inability of most Telco service providers to meet the flat frequency response and phase
matching requirements of the pair of audio circuits. Furthermore, in many countries wide‑
band analog circuits have become unavailable or their cost is prohibitive. On the other
hand if the “wired” STL is a dedicated (and equalized if necessary) pair of circuits that
is under the station’s full control it may be acceptable.
Arbitron People Meter (PPM)™
Field experience has been that Wheatstone processing algorithms favorably pass the
data watermarking scheme used in the Arbitron People Meter rating service technology,
regardless of the aggressiveness of the processing being performed. The X1 algorithms
are no exception. The X1 hardware also adds the additional benefit of inserting the PPM
watermark and associated hardware towards the back of the processing for both the HD
and FM audio paths. This eliminates the need of having an external AGC to feed consis‑
tent audio to the PPM encoder. You can now use the internal AGC in the X1 to do this
while allowing the PPM encoder to insert the watermark AFTER most of the processing.
AC Power Considerations
Please note that in order to enhance its long‑term reliability X1 has no power switch
(switches usually become intermittent over time without regular use).
X1 accepts AC line input voltages between 90 and 260 VAC, 50 or 60Hz. Power
consumption is under 100VA.
Although aggressive AC input filtering is utilized on the AC power input it is always
advisable to use external surge protection and an uninterruptible power supply (UPS)
wherever possible, especially where the AC power quality can be in question, such as at
a remote transmitter site.
Power conditioning, surge suppression, and even power backup devices are wise
investments when using sensitive modern electronic devices. X1 is, after all, a highly
specialized “computer.”
The use of a UPS (uninterruptible power supply) is usually recommended and will
protect X1 from short duration power interruptions and glitches which might otherwise
signal it to reboot. When X1 reboots there will be a loss of audio for approximately 15
seconds.