Federal bureau of investigation
Whenever the FBI has a case to work on, they'll brief their staff on paper, every member of that briefing gets his own 'briefing-pack'.
Furthermore the FBI discusses situations face to face. Also, when on a mission, the FBI uses handsigns to communicate without noises to prevent other people from getting secret information or clues.
The FBI uses practically everything known to mankind when it comes to technology. This variates from a simple TV to walkie-talkies and earplugs in order to communicate with them. The FBI wouldn't be the FBI if they didn't have secret communication tools such as camera pens to investigate their surroundings. The FBI is a organisation that operates very secretly, so you can imagine that the tools they use aren't known to common citizens.