A walkie talkie is a handy, portable transmitting and receiving device that makes it easy for two or more people to communicate with each other. While they're also enjoyed as toys by children, they're commonly used for a whole range of professional applications too. Emergency services, security personnel, retailers and event staff all commonly use them, for example. A walkie talkie works using the 'half-duplex' principle. This means when one person has the transmitter button pressed, the others can only receive a signal which prevents crossed communications.