| 摘要 |
<p>Mobile telephones are often used during transport involving risk, and in that case to call for help. However, the mobile telephone may be blocked by the perpetrator of a crime. The present invention solves this problem since, whether it is in use or not, a mobile telephone continuously emits a signal. An alarm will be triggered in the absence of a signal at a receiving unit, which receiving unit may be an alarm centre or an Internet</p> |
