Whenever you're on a call, the iPhone makes it pitifully easy to perform stunts like turning on the speakerphone, putting someone on hold, taking a second call, and so on. Each of these is a one-tap function.
Here are the six options that appear on the screen whenever you're on a call.
Tap this button to mute your own microphone, so that the other guy can't hear you. (You can still hear him, though.) Now you have a chance to yell upstairs, to clear the phlegm from your throat, or to do anything else you'd rather the other party not hear. Tap again to unmute.
Sometimes, you absolutely have to input touch tones, which is generally a perk only of phones with physical dialing keys. For example, that's usually how you operate home answering machines when you call in for messages, and it's often required by automated banking, reservations, and similar systems.
Tap this button to produce the traditional iPhone dialing pad, illustrated in The Keypad. Each digit you touch generates the proper touch tone for the computer on the other end to hear.
When you're finished, tap Hide Keypad to return to the dialing-functions screen, or tap End Call if your conversation is complete.
Tap this button to turn on the iPhone's built-in speakerphone—a great hands-free option when you're caught without your earbuds or Bluetooth headset. (In fact, the speakerphone doesn't work ...