Comment Re:LED Pay Phone Tap (Score 1) 179
Having seen devices like these in the past, chances are it is a telecommunications device for the deaf, in this case designed for payphones.
I presume there would have been instructions printed on the front of the device that would go something like this: If a deaf or hard-of-hearing person wants to make a phone call, they insert coins, then dial the number of interest. When they see the light on the other end flashing randomly (i.e. not a ringing or busy signal), they can press a key on the payphone's touch-tone pad a few times to cause a prerecorded voice to announce the TTD's presence.
If the party on the other side starts typing with their own Teletype device, the TTD on the payphone will then open up to reveal its own display and keyboard. The reason it cannot be opened up without hearing a remote TTD first (at least on the units I have seen) is to prevent vandalism on what is obviously an uncommon and slightly expensive piece of equipment.