Push-to-Talk – PTT is also known as ‘walkie-talkie’ service. PTT groups of mobile phones are pre-defined as members of a group who all have a specialized mobile phone with a push button. Depressing the push button allows the user to automatically record and play a message on the other group members’ mobile speakerphones. PTT users can reply to all other group members in a similar fashion. Useful in construction, some retail environments, warehousing and other applications where users are mobile, any member of the group has specific information or can get specific information and paging systems aren’t appropriate.