remarkable opamp

Ummm... when was the last time you actually had wireless security? I've been monitoring mobile phone calls from when you had to setup a call with a mobile operator, IMTS, and analog cellular using call progress detection. With 2G (GSM, CDMA, TDMA) it was still possible with the right equipment, but I didn't have it or need it. 3G can be hacked with a $1,200 receiver and OpenBTS software: I haven't tried it. No clue on LTE hacking.

The with "many small cells" is the backhaul. Somehow, the data needs to go back to the cellular provider. That's usually done with fiber on the poles which tends to be expensive. There's also a problem with disappearing phone poles as municipalities underground their utilities.

At this time the topology of 5G systems is still an open question. The FCC has allocated 3 band for vendors to run tests and see what can be done. 700MHz won't handle the expected traffic, 3.5GHz doesn't have enough bandwidth, and 28/38GHz is currently science fiction but has plenty of available bandwidth. Of course, that hasn't stopped the FCC from auctioning off the frequencies before the manufacturers have a clue as to what can be done:

A typical well insulated house, with foil backed insulation in the walls, will need an access point in every room at 28/38GHz.

Samsung claims 2 km (1.2 mile) range at 1Gbit/sec on 28/38GHz using high gain and highly directional antennas at both ends. If that's for real, which I doubt, then 5G may actually be practical. However, that was press released in 2013 and I haven't seen any new numbers since then from Samsung.

Licensed air space is not free if the cell company is passing along their spectrum auction costs to the users.

Air space crowded. If you can see another users radio, they are a potential source of interference. Basically, you can have only one transmitter belching RF in an "air space" at a time. It's much the same as the size of a cellular "cell". Indoors, an "air space" can be as small as one room. From a rooftop, it can have a radius measured in miles. As you get higher and higher, the number of potentially interfering users on the same frequency drastically increases.

pt?

Visual monitors aren't intended to. Braille monitors have little pins that pop up to produce Braille representations of the character string fed into them.

The one I worked on some twenty years ago had piezo-electric strips to push them up, and the project was to detect the back emf from the finger pushin g any pin down. Seemed to work, but I don't know if it got put into product ion.

I found a paper on a narrow Braille display that scanned the characters acr oss a stationary finger, which worked for the developer (or so they claimed ). Humans reading Braille readers apparently scan with both hands at once, with the scanning fingers going left and right, which is impressive, and wo uld make a single-finger serial display a bit slow.

A 360 cell Braille display has been developed, containing many motors:

BTW I agree about the faint thin light grey characters.

A particular bete noire of mine is a local supermarket pasta. The /only/ information you require is the cooking time. So they put that in 2mm letters on the back of the packet - in light yellow on dark yellow background.

Very arty. Very farty.

Actuators rather than motors. My guess would be the gear that adjusts the flying height of the optical sensing head in the CD drive rather than anything that looks like an electric motor (linear or rotary).