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In my house CallerID phone manual there was an option like the date and time can be set when CallerID is active and for a particular type (I am not able to recall whether it was mentioned as FSK or DTMF).

I would like to know where can we find the full details of what this FSK or DTMF stands for and how to find out whether my telephone exchange (Chennai BSNL) is what type. I called my CustomerCare but they are unable to reply in that.

Admin/Moderator: I could'nt judge which TA would be appropriate for this question and hence I am requesting you to kindly help me out in deciding the most appropriate TA and move this question over there since I feel that this would be a useful information, once responses are recieved to this question.
4 Solutions
FSK is frequency-shift keying
DTMF is Dual-tone multi-frequency
This is one quite good explanation of the second:
http://en.wikipedia.org/wiki/Frequency-shift_keyingThey all contain a lot of links as well... so just review them..All the standards and so on are linked.  

As fpr determining what type is your phone exchange: I am a bit confused.
As far as I recall DTMF is a type of FSK ( of MFSK to be correct). So what do you mean?
DTMF stands for Dual Tone Multi Frequency
FSK stands for Frequency Shift Keying

DTMF assigns a specific frequency with two separate tones to each key (0-9) and then the keys are easily can be identified by the system.

Example:~ I can give you an example/ application of DTMF on mobile. On a BSNL(or any) mobile you can know the balance by dialing 123 followed by pressing the key 1. Now just dial 123 on mobile & when the call is connected you can click "Option" (it may varies set to set ) on your cell. Then click "Send DTMF" now it will prompt to input a number here press "1".

Also you can do the same if you're using IT Card (BSNL) where you've to enter about 16 digits. You can save that 16 digit number at your phone book (mobile or land) & then as previous example you can put those numbers by sending DTMF. So that you dont' have to enter those numbers each time. After validating when you'll be asked to enter the phone no. you want to dial, you can again use DTMF.

Hope this helps
Here you may find some more info on what you need:


and, yes, your telco is the only one appropiate to answer what standard they use...
DTMF uses a signal with two frequencies sent at the same time. The combination of frequencies is determined by which key is pressed and they are sent through the line and then separated at the end point. Each combination of 2 frequencies equals a function (a digit or sign). The number of frequencies used is limited. In Sweden we usually interpret the acronym as "Dual Tone Multi Function" signalling (english is often used in techie language).

Frequency shift keying is similar to some extent, as a combination of frequencies are used for coding purposes. Only in FSK the tones are sent after one another, not simultaneously.

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