Q Our son keeps signing up for expensive chat line services on his mobile phone. Can we prevent him from subscribing to these?

NS, via e-mail

A To some degree, yes. Most mobile phone networks offer call-barring features that can prevent outgoing or incoming calls from premium rate or other undesirable numbers.

You would need to set up this feature first on your son’s phone, so check with his network operator to find out how to do so. What complicates the issue is the sheer variety of ways that premium-rate services can take payments, including reverse charge calls or SMS texts.

Some networks offer more advanced levels of protection than others, though SMS-barring is extremely rare. It’s also worth checking the manual of his mobile phone as some of the latest models have a call-barring feature built in.

Phonepayplus, the UK regulator of premium-rate telephony services, issued new consumer guidelines for these subscription services in January. See www.tinyurl.com/n87jlw for details.

Q How can we easily and cheaply convert our printed parish magazine and other local historic material into PDF format to distribute and sell?

RL, Newton Abbot

A You will need to buy a scanner to convert your material into digital form. Get a model that can convert scans directly into PDFs without you having to open them on a computer, such as the Epson V300 (www. tinyurl.com/nu7ksz). If you need to process a lot of documents, invest in a scanner with a sheet feeder.

The “scan to PDF” software that comes with these scanners often allows you to create electronic text versions of the scans too, which you can reformat into other documents. Another way to convert them to text is to upload the PDFs to a website and wait for Google to do the hard work for you. When you can find them on a Google search, click on the “View as HTML” option and it will open up a cut-and-pasteable version of the originals. Sadly, neither method will work with hand-written or illegible material.

Q Do I need to connect the coaxial aerial cable to every piece of hardware attached to my television, or can I rely on the Scart sockets to send the TV signal between machines?

MH, Staffordshire

A Scart and coax sockets do two different jobs. The Scart sockets are designed to transmit video and audio signals from one box to another, including to your television; coax feeds the broadcast signal from your aerial to a tuner/receiver. The simple rule is that every device that has a tuner in it, such as a VCR, personal video recorder (PVR), television or set-top box, needs to have a broadcast signal input fed to it, either through the aerial coax or a digital cable connection — but only if you are going to use it directly.

So, if you only ever use your PVR to record whatever’s on TV at the time, you don’t need to feed a signal to it. But if you use it to record TV while your set is switched off, the coax should go into the PVR, which then relays the feed to the TV over Scart. The same logic means you do not need to plug your aerial cable into your TV if you have a satellite or cable box attached.

Tech tip - How to use a phone as a broadband router

Many phones can operate as a modem, allowing you to use their 3G signal to link a computer to the internet. The connection may not be the fastest — typically between 300kbps and 750kbps, which is about a quarter of the speed of most people’s broadband — but it’s enough to send e-mail and view websites.

You’ll need to check the manual to see whether your phone has a modem in it, then set it up using the software supplied with the handset and connect it to the computer via a USB cable. Setup can be a little fiddly but needs doing only once.

If you have a smartphone with wi-fi, it’s easier to set it up to share its 3G connection and create a wi-fi hotspot. Owners of Windows Mobile phones — which include many HTC and Samsung models — can do this by downloading and installing WM WiFi (£17 from www.wmwifirouter.com); Nokia smartphone users can do the same with the excellent JoikuSpot Premium software (£13 from www.joikushop.com).

E-mail your technical queries to dontpanic@sunday-times.co.uk