What Is The Difference Between...

[Guest stuck]

What is the difference between analogue and digital signalling

 

and synchronus and asynchronus transmission

 

 

thanks for the help whoever answers my question :-)

[SupportTeam]

Analog lines are the 'normal' telephone lines - sometimes known as POTS lines (Plain Old Telephone Service).

 

Digital lines come in PRI and BRI types - the PRIs carry 24 or 30 lines each (T1 has 24 lines and an E1 has 30 lines) and BRIs carry 2 lines each - you should speak with your phone company to see which lines they can provide.

[Guest in need of help]

What is the difference between digital and analogue signalling?

[SupportTeam]

They're just two different ways of sending information over the wires...

 

How many calls does your system need to answer/handle at the same time?

[ktruk]

Analog signalling uses "in-band" tones (DTMF) and other signals, like hook-flash, to control the call sequencing. In-band means the tones and other signals can be heard on the same line with the voice, ie, the signals are carried along with the audible voices. To control the call sequences the telephony card/modem needs to be able to distinguish what is voice from control signals. Means of detection vary and adequate processing is dependent upon how clear the signals are, their timing and frequencies, and whether the telephony system is properley setup to match the actual signals on the line and how good the electronics actually are. Hence, the constant battle to detect the right disconnect tone, ring-back signals and other control signals present on the line. Thats why VoiceGuide recommend dedicated quality hardware as cheap modems, while voice capable, are just not adequate at detecting the in-band signalling reliably and don't offer any opportunity to tune the modem settings to match the signalling used on any particular range of calls.

 

Now, Digital signalling is different and is usually "out-of-band", what this means is that the digital circuit separates out the signalling from the audio data and sends it down a separate audio and signalling channel(s). The benefit of this that the signalling is distinctive and not confused by audio signals, therefore, the telephony systems can control the call without having to wait to make up its mind whether a cough on the line is a cough or a hangup command. By digital, what is usually meant is ISDN, which carries the audio down "B" channels and the signalling down "D" channels. A digital ISDN telephony card can listen to the audio on the B channel and act upon signalling on the D channel. Due to the clear and explicit nature of the D channel signalling, calls are setup more quickly and have more flexibility, since this channel can carry more information more quickly than in-band signalling.

 

Hope this helps !