Tone boards are standard equipment on some scanners. Although it is true that numeric codes are used a lot in military and paramilitary radio communications, these codes are easy to learn with just a little practice. Besides, many transmissions are transmitted in plain language in some jurisdictions, making mastery of alpha-numeric codes unnecessary. Explanations of the codes can be found on the net or in scanner books. The next most interesting voice radio transmissions are phone calls.
People say the damnedest things on the phone.
They lie, cheat, and steal for everyone to hear. They have real live phone sex that makes reading the Penthouse Forum seem like Garfield cartoons. I was once involved in a court case involving my family and a governmental agency. One day an envelope was delivered to my house with a cassette tape in it. The scanner buff involved had accidentally stumbled across the conversation and was alert enough to realize what being said and to record it.