Looking for a unique way of communicating at your hackerspace? Why not hack used Sprint/Nextel phones into free “off the grid”, relatively secure walkie talkies? Here’s a cool keyboard trick which reportedly works on Sprint/Nextel Motorola i315, i325 models and some other Motorola phones, which puts the phone into “Direct Talk” (a/k/a MOTOTalk) mode. This allows it to function as a walkie talkie without going through the cellular or Nextel “Direct Connect” networks.
A chart containing these little known keyboard sequences is available on the Sprint/Nextel site. There are ten user selectable channels and 15 sub-channel codes per channel. Users on the same channel/sub pair can monitor and communicate with other users on the same pair.
Direct Talk mode allows the phone to transmit directly to other (similarly enabled) phones within a short distance. It uses the 900 MHz ISM band and spread spectrum modulation, which is unable to be monitored by scanner radios. Nextel states the range as up to 6 miles, but given the low transmit power used by these devices it could be considerably less. It should work on any previously activated Sprint/Nextel handset which recognizes the Direct Talk feature, and since it’s marketed as working even where network service is not available it should work with phones not currently on a paid subscription. The phone must have a SIM card installed. Inexpensive used handsets are often available on Ebay and other sites, so give it a try!
NOTE: This is not a hack to get free cellular service or free “Direct Connect” network usage.