1. Make sure to be in the main screen (press “esc” 2 times if unsure)
2. press the “▶▶▶” key (menu)
3. type: “***76#”

Prerequisite: Phone turned off

1. Hold key 4
2. Turn phone on still holding key 4
3. Hold Key 4 until menu appears

This menu holds tests for Keyboard, Display and Audio, Reset to Factory Defaults, DECT Monitor, Headset (MT-F only), Sensors (C5 only)

1. Hold key 5
2. Turn phone on still holding key 5
3. Hold Key 5 until menu appears

This menu holds a radio test mode. No idea what this is good for.

1. Hold key 6
2. Turn phone on still holding key 6
3. Hold Key 6 until menu appears

This menu holds tests for ambient lighting, accumulator, infrared (if present), display, colors, RAM and proximity sensor

1. Hold 1 + 4 + 7 while powering on the phone
2. Enter the key sequence 76200
   • This is not true for Gigaset 3000 Comfort.
   • Gigaset 3000 Classic/Comfort service manual: Here (PDF).
   • It says the key sequence for Gigaset 3000 Comfort is 46395