Jerry Avins wrote:
Dave Platt wrote:
In article . com,
Radium wrote:
I'm curious to why there are no purely-analog devices which can
record, store, and playback electric audio signals [AC currents at
....
The net result is that an audio CCD is capable of
storing a
decent-quality signal for only a few tens or hundreds of milliseconds,
from input to output.
Another sort of a purely analog signal-storage device,
with no moving
parts other than the electrons which convey the signal, is a simple
length of transmission line (with perhaps some amplifiers mid-way).
....
Come on, Dave, a CCD is a digital device, subject to
aliasing.
CCDs are analog devices, with an analog voltage output.
The fact that they are commonly used as the sensor in
digital cameras results in the output of a CCD virtually
always going directly (well, after a bit of signal
processing for things such as white balance, ISO gain,
etc.) to an analog-to-digital converter that digitizes
the analog signal.
The charges represent the signal at a
particular instant of its average over a particular
interval. (My CCD digital camera can take time
exposures.) A CCD's content may not be quantized in
amount, but it is quantized in time. In a camera, where
the charges pertain to individual pixels, the result is
also quantized in space.
But none of that quantization changes the fact that the
device itself has an analog output.
--
Floyd L. Davidson http://www.apaflo.com/floyd_davidson
Ukpeagvik (Barrow, Alaska)