is cellphone keypad a DTMF style?

Status
Not open for further replies.

W_Heisenberg

Full Member level 4
Joined
Feb 27, 2011
Messages
217
Helped
6
Reputation
12
Reaction score
6
Trophy points
1,298
Location
Boston
Activity points
2,575
I know it is absolutely not dial pulsing mode, but is it then DTMF?
 

Are you referring to "cellphones" or GSM system? GSM dial signals are primarly not DTMF, but can be converted to DTMF tones by the mobile switching center when transferring key presses during voice calls. What are you exactly asking for?
 

Well, I think cellphone nowadays are all GSM or CDMA.

Could you tell me what kind of tones are used in GSM? and CDMA?

In other wordes, DTMF is only via phones? like home phones?
 

Cell phones send dialling information out as digital data, not as tones.

Most do also generate DTMF tones but this is so they can be used to talk to remote systems (call centers, home banking etc.) which need to accept audio tones because the call could be coming from a landline phone or autodialler. DTMF isn't actually used until the call is established and the audio channel is opened.

Brian.
 

I suspect the reason texting has become so popular is because cellphone audio is so bad nobody can understand what the other is saying. Since keystrokes are sent as data, the same kind of bit-count error correction that's used on the internet comes into play.
 

When designing or selecting a new phone, publishing or using phonewords, one should be aware that there have been multiple standards for the mapping of letters (characters) to numbers (keypad layouts, as with keyboard layout) on telephone keypads over the years.
 


:idea:

fair.
 

Seems like the original question has been answered. The thread seems to attract off-topic posts now and should be closed, I think.
 

Actually, the question has not been answered yet. The original analog cell phones did use DTMF. Present-day digital ones do not. In fact they cannot. The vocoders they use are incapable of reproducing DTMF tones, just as they are incapable of reproducing music.
 

Actually, the question has not been answered yet.
Click to expand...

I'm under the impression that it has been clearly answered. Like other digital communication systems, e.g ISDN, GSM doesn't use any dial tones. All connection related data (a lot more than just dialed number) is transmitted through the digital protocol. As said, even the simulated DTMF signals available during a voice call are not actually send as tones but generated by the mobile switching center when transferring to a wired connection.
 


In that way, what is the name for cellphone so-called "dial tone" and how it is produced?
 

I wasn't aware they had dial tones. I thought you just punched in the number and pressed "send". Or do you mean the "ringing" tone you hear after that? That is a reproduction of the actual analog ringing signal, at least if you are connecting with an analog based phone network. Since that is basically a single tone being rapidly switched on and off, the vocoder can reproduce it. If you're talking cellphone to cellphone in the same network, there's no A/D, D/A conversion going on, so it is generated in the phone itself.
 

In that way, what is the name for cellphone so-called "dial tone" and how it is produced?
Click to expand...
Considering the previous discussion, the question should be clearer. Are you talking about GSM dial commands or simulated dial-tones sent to an analog phone?
 

Status
Not open for further replies.

Similar threads

Menu
Log in
Register
Cookies are required to use this site. You must accept them to continue using the site. Learn more…