Most recent model Oki brand cellular phones have an undocumented feature that you can amuse yourselves with. If you enter the proper commands, your phone will work like a scanner and you can listen to the conversations of others.
Try this at home kids!
-Press keys 7 and 9 simultaneously.
-Press menu, send, end, rcl, sto, clr sequentially
-Press keys 1 and 3 simultaneously
You should now be in a special test menu.
If you have a portable you must either:
-press #, 7, 6, snd
-press #, 7, 7, snd
(one command routes output audio to the earpiece, the other command routes the output audio to the ringer, which is louder)
-Press #, 7, 9, snd
(this command lets you enter certain subsequent commands with one keystroke)
-Press 2 (this command unmutes the receive audio)
Your phone should now be scanning between channel 0360 and channel 0800, the last two digits (02) represent the scan speed (01 is faster 03 is slower etc). Pressing # stops the scan, pressing # again resumes the scan. To scan with new parameters press clr and repeat the last step.
If you're only interested in on specific channel, say channel 100, press 9,0,1,0,0,snd
The real fun however, is flipping the carrier on and bumping the person on the land-line end of the conversation off the cell, and telling the mobile phone user to please deposit 25 cents or pretending to be at the location where the land line user is and improvising from there.
After you have executed the #,7,9,snd command, simply pressing the 1 key will turn the carrier on. Pressing 1 again will turn the carrier off. In my post I said you could cut the land-line party out of the conversation, I got this backwards, if your signal is stronger than the mobile user, you will be connected to the person on the land-line end of the conversation. This is easy to do because, by default, the phone operates at the highest power level in test mode, whereas in actual use the cell tells the phone at which of 8 possible power levels to transmit at.
Even if you are successful at blocking the signal of the mobile user, there are a couple of things you need to do in order for the person on the land line end to hear your voice. In order to be able to reuse frequencies more often, many radio systems use 'tone-coding' to distinguish between different sets of users who share the same frequency. In cellular systems adjacent cells don't use the same channels, but every 2nd of 3rd cell might resuse the same channels. In order for cells to be able to determine that a signal originated within the cell rather that from a nearby cell, cellular transmissions are coded with one of 3 possible background tones. Each cell recognizes one of the 3 tones, it is a matter of trial and error to determine which one. Pressing 6 followed by 0,1,2 or 3 as an argument sets the tone to be used during transmission (I forget whether 0 or 3 means tone off).
In order for the other person to hear you, you must also press the 3 key, this unmutes the transmit audio, pressing 3 again remutes it.
It is not possible to get two cell phones to talk directly to each other. This is because cell-phone conversations are duplexed, phones are simultaneously transmitting and receiving on different frequencies.
This means that cell-phone transmit freq = cell receive freq and cell-phone receive freq = cell transmit freq.
I don't have an actual tech manual, but just some scattered notes, I'll try to dig up some more goodies.