Activate RBS
(Note: pause means the * key held in until box appears)
To activate RBS type: [pause] [pause] [pause] 1 1 3 [pause] 1 [pause] [ok]
You now have to press the [MENU] and scroll to the 'Eng Field Options' function with the keys, and enable it.

De-activate RBS

To de-activate RBS type: [pause] [pause] [pause] 1 1 3 [pause] 0 [pause] [ok]
This only works with some versions of software.

These countries has been reported working:

ES, AU, NL, BE

What's the use of RBS:

Get Distance From Base Station - Place a call, when it is answered, press [MENU] until 'Eng Field Option' is displayed, press [OK], select 'Active Cell', press [OK], press [MENU] until 'Time Adv xxx' appears, where xxx is a number. Multiply this number by 550, and the result is the distance from the RBS (Radio Base Station), in meters.

Get Signal Quality - press [MENU] until 'Eng Field Option' is displayed, press [OK], select 'Active Cell', press [OK], press [MENU] until 'C1' appears. This is the signal quality. If it becomes negative for longer than 5 seconds, a new cell is selected.

Pin Outs

Numbered right to left, keypad up, battery down looking

1. Audio Ground
2. V+
3. True data (TD) (input)
4. Downlink - Complimentary data (CD) (input)
5. Uplink - Return data (RD) (output)
6. GND
7. Audio Out - on/off
8. Audio In
9. Manual Test - ???
10. Battery Feedback
11. Antenna connector