Half/full duplexing goes back much further. Half duplex implies a shared
media. Often only one can speak at a time. A good analogy would be radio
communication where when one is done speaking they use a key word such as
"over" to indicate that the other may speak. With full duplex both can
simultaneously transmit. In telephony this often referred to a four wire
circuit where the two wire circuit went to a hybrid coil circuit that
converted it to four wire. Two for transmit, two for receive. Analog can
amplify in one direction only - thus the need for four wire circuits for
interoffice trunking.
The next step is to modulate voice traffic with different carrier
frequencies and multiplex the sum over the same four wires. The good news is
that many calls can share the same wires. The bad news is that the
amplifiers can't tell the difference between signal and noise. So long
circuits have increased noise.
The solution to noise was to digitize the signal and periodically regenerate
it. Anything below a certain threshold is considered noise and is rejected.
This was the beginning of TDM, Time Division Multiplexing, aka T-1s.
> -----Original Message-----
> From: Joseph Ezerski [mailto:[EMAIL PROTECTED]]
> Sent: Wednesday, October 18, 2000 12:21 PM
> To: 'Daniel Cotts'
> Subject: RE: Is TDM full duplex or half duplex
>
>
> Correct me if I am wrong, but isn't duplexing an
> Ethernet-only concept?
>
> Joe
>
> -----Original Message-----
> From: Daniel Cotts [mailto:[EMAIL PROTECTED]]
> Sent: Wednesday, October 18, 2000 9:02 AM
> To: 'Jeff Lodwick'; [EMAIL PROTECTED]
> Subject: RE: Is TDM full duplex or half duplex
>
>
> TDM to me means T-1 and similar technology. It is full duplex sending
> seperate transmit and receive bit streams.
>
> > -----Original Message-----
> > From: Jeff Lodwick [mailto:[EMAIL PROTECTED]]
> > Sent: Wednesday, October 18, 2000 8:48 AM
> > To: [EMAIL PROTECTED]
> > Subject: Is TDM full duplex or half duplex
> >
> >
> > Hi everyone,
> > Does anyone know if Time Division Multiplexing will work with
> > only half
> > duplexing or only full duplexing or both. Jeff Lodwick MCSE/CCNA
> > ______________________________________________________________
>
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