Help File

QI'm taking my iPhone on an international trip and don't want to get hit with any roaming charges. How can I shut off the phone but keep WiFi on?

AThis is a good idea, considering voice calling can run well over a dollar a minute overseas -- even for calls that you let go straight to voice mail. International data access is still more expensive, and AT&T Wireless's "Data Global" add-ons -- starting at $24.99 a month for 20 megabytes -- are no bargain either.

Fortunately, the iPhone's software blocks data usage on non-AT&T networks. To verify that yours still has this setting, tap the Settings application's General heading and then its Network heading; on that screen, the "Data Roaming" switch should be off.

To block voice calls too, the simplest remedy is to remove your iPhone's SIM (subscriber identity module) card. Take one end of a small paper clip and poke it into the small hole next to the headphone jack, and a plastic carriage holding this small card in place will pop out. Tuck the card away where you won't lose it, and your iPhone will only be able to speak WiFi.

I know that some TV stations will stop their analog broadcasts on Tuesday. Do I need to do anything to get my digital TV ready for that?

Some stations making the digital transition before the federally mandated deadline -- just pushed back from Tuesday to June 12 -- will be able to upgrade their digital signals once they take down their analog transmitters. So you'll want to have your TV rescan the airwaves for any changes to these channels.

To do that, press the "menu" button on the remote for your TV (or digital converter box) and click around until you see a command like "scan for channels" or "add digital channels."

Rob Pegoraro attempts to untangle computing conundrums and errant electronics each week. Send questions to The Washington Post, 1150 15th St. NW, Washington, D.C. 20071 or robp@washpost.com. Turn to Thursday's Business section or visit washingtonpost.com anytime for his Fast Forward column.