Fortunately, there are some URLs that will help us. The first de facto standard (copied from the Japanese i-Mode standards) is to use the
tel:<phone number>scheme. This is called the i-Mode format:
<a href="tel:+1800229933">Call us free!</a>
Some devices also allow sending DMTF tones after the call has been answered by the destination. This is useful for accessing tone-controlled services, helpdesk systems, or voicemail; you can say to the link, "call this phone number and, when the call is answered, press 2, wait 2 seconds, and then press 913#". You do this using the
postdparameter after the number: the syntax is
;postd=<numbers>. You can use numbers,
#(using the URL-encoded
%23value), as well as
pfor a one-second pause and
wfor a wait-for-tone pause:
<a href="tel:+1800229933;postd=4">Call us free!</a>
This function doesn't work on all mobile devices, but on devices that don’t understand it, the primary telephone number should at least be called. The compatibility list for this feature is complex, and I don’t recommend relying on it.
If the user activates a call link she will receive a confirmation alert asking whether to place the call, showing the full number so she can decide (see the image below). This is to avoid frauds tricking the user into calling another country or a premium number.
Note: I recommend inserting the phone number in the international format: the plus sign (+), the country code, the local area code, and the local number. We do not really know where our visitors will be located. If they are in the same country, or even in the same local area, the international format will still work.
Although the table below shows that it is not as well supported as
tel:, the other way to originate a call is using the WTAI standard, via the
wppublic library and the
mc(make call) function:
<a href="wtai://wp/mc;+1800229933">Call us free!</a>
WTAI also accepts a link to be used while the call is in progress, but this is useful only if the user is in hands-free mode or using a headset. This link can include tones to be sent to the destination as if the user had pressed them on the keypad, specified using the
sd(send DTMF tones) function.
Note: The BlackBerry browser automatically detects phone numbers and email addresses and converts them to links. If you don’t want this feature, you should use the
<meta http-equiv="x-rim-auto-match" content="none">. Safari also has its own metatag for the same action:
<meta name="format-detection" content="telephone=no">.
iDEN networks (like Nextel) use radio packets to make internal calls inside the network. If you are working with customers of such a network—for example, for an intranet—you can allow users to launch internal calls to other members of the team (or external calls) using the Direct Connect URL scheme (
dc:<number>). This is compatible with BlackBerry iDEN devices:
<a href="dc:5040*0077">Ping John</a>
Note: Some models present users with a submenu when they click a tel: link so they can choose whether to place a voice-only or a video call (available in 3G systems). Some Japanese phones also allow you to specify that a link should initiate a video call, using the protocol
The table below lists which voice call URI schemes work with which platforms.
|Browser/platform||tel: compatibility||WTAI compatibility|
|Nokia Series 40||Yes||Yes|
|NetFront||Yes, for call and add to contact manager|
|Internet Explorer||Yes, for call, SMS, and add tocontact manager|
|Motorola Internet Browser||Yes, for call, SMS, and add tocontact manager|
|Opera Mini||Yes (unless Java MIDP 1.0 device)||Yes (unless Java MIDP 1.0 device)|
Note: The iPod Touch, a non-phone mobile device, doesn’t allow voice calls. Instead, it shows a prompt to add the phone number used in the
tel:link to the phonebook.
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