We always tell our participants that if they are calling for assistance and end up leaving an answer phone message that they also send a text with the same information afterwards. The reasons for this are:

1) We may pass through an area of phone signal or get a fleeting, weak signal meaning that we will see we have a message but be unable to listen to it. If it comes in as a text we can read the message even if we don't have signal when we come to read it.

2) A text message will transmit exactly how you send it. An answer phone message may be distorted due to poor signal or high wind at the callers location. The caller cannot tell what the recipient will hear.

This is an MP3 of an answer phone message left by a team requesting urgent medical attention and demonstrates the problems leaving messages on an answer phone. As it happened one of our members of staff was about 20 meters away behind a wall as this call was being made (though he couldn't see or hear what was going on) and was on the scene about 2 minutes later to cries of 'You're like ninja's you lot' .

When training groups in emergency procedures we play this clip to them to illustrate the point.