I've seen this done on a window - the vibrations of the voices in the rooms create a very small vibration in the window panes which can be converted reasonably easily back into sound. ----- Original Message ----- From: "Denny Esterline" To: Sent: Wednesday, March 31, 2004 9:43 AM Subject: Re: [EE:] Phototransistor as Serial Input? > This is only indirectly related, but I remember reading an article > *several* years ago about a technique that was being used to spy on people. > IIRC they used a photosensor and extensive optics (telescope) and measured > the reflected light output of a monitor/tv. With enough processing they > could reconstruct the image displayed on the screen (well enough to read > text), even without a direct view of the CRT, and at large distances (1/2 > mile?). Something about the refresh rate and the v-sync pulses to > synchronize off, and just an ambient light level correlating to a pixel > intensity. > > If they can do that, surely you can transfer a few bytes. > > -Denny > > > > Hi Folks, > > > > I'm designing a little PIC-based gadget that will have 8-10 variable > paramaters that I'll store on-board the PIC. > > I'd like people to be able to configure this gadget by means of a PC > program. The program will have the nice interface and do the > > necessary calculations, but ultimately the 8-10 8-bit variables that will > result need to be delivered to the PIC. I want to keep > > cost and weight down, so my idea is to use a phototransistor on the PC > board to watch a "flashing box" on the monitor that sends > > serial data from the PC program. The user would hold the board up to the > monitor, hit a key, and the data would be transferred. > > > > Has anyone done anything like this before? I think it would be relatively > straight forward, but I'm not sure how to filter and > > massage the input from the phototransistor. Any help would be > appreciated. > > > > Thanks, > > > > Jeff > > > > -- > > http://www.piclist.com#nomail Going offline? Don't AutoReply us! > > email listserv@mitvma.mit.edu with SET PICList DIGEST in the body > > > > -- > http://www.piclist.com hint: To leave the PICList > mailto:piclist-unsubscribe-request@mitvma.mit.edu -- http://www.piclist.com hint: To leave the PICList mailto:piclist-unsubscribe-request@mitvma.mit.edu