Last night my Samsung BlackJack stopped making and receiving calls. That’s generally not a good thing for phones to do (or not do). The display showed that I was connected to Cingular and that I had strong signal strength, but any calls placed would hang up immediately, and if anyone tried to call me the calls went straight to voicemail.
I removed my SIM card and tried it in two other devices (Cingular 8125 and Treo 650), and both were able to make and receive calls. I then put the SIM card back into the BlackJack, but no luck.
My initial assumption was that the device had died. But while driving around this morning I found that while the phone did not work at home, it did work a couple of miles away. And of course, those other devices worked properly at home. So it was not the phone.
The problem? Apparently Cingular was having issues with their 3G network in some locations. A Cingular rep told me that there have indeed been sporadic issues with 3G, but that these were being resolved. Those other devices are not 3G, they use the older GSM network, and so they worked. But the BlackJack connects to 3G networks if they are available, and falls back to GSM only if 3G cannot be found, and so it would not work because 3G was available (even though it was not working properly).
Which means that I really needed to find a way to tell the phone to not use 3G even if it is available, just in case. And of course, there is no menu option for this. But after some research I found a control code sequence which displays an Admin Settings screen which can be used to do exactly what I needed.
Here’s what you need to do:
- Enter phone number *#1546792*#
- Select menu option “3 Network & Call Settings”
- Select menu option “5 Network Mode”
- To force GSM select the “GSM” option, to reenable 3G support select the “Auto” option
And that’ll do it.
Oh, and apparently, 3G use consumes far more power. So, if you are low on power, and are not actively using high-speed data connections, temporarily switching to GSM using the technique just described could help.