[TriLUG] Re: Phone to use with PC

[Scott G. Hall]

sjackson at radarfind.com wrote:
> Easiest way I know is to use a Nortel/Aastra Meridian 9617 USB phone. 
> Plugs right in to the PC's USB port, and either the phone or the computer
> has full control over the comings and goings.

I don't want a phone handset!!  Quite the contrary, I want to use the same
headphones I listen to music from the PC as my earpieces, and the microphone
over the monitor as the mouthpiece.  In ham-radio, this is called a "phone
patch".  In the broadcast industry, it is called a telephone hybrid (based
on the use of hybrid transformers), such as those used for talk-radio shows.

On a standard telephone POTS line, there are several signals on it at the
same time: the incoming audio, the outgoing audio, a high-voltage ring
signal, and a DC voltage used to power handsets.  After blocking the DC
voltage, and shunting the ring voltage, a hybrid transformer set separates
the incoming from the outgoing audio (they are blended or "mixed" together).

A standard modem already has the circuitry to "hybrid" the signal, and DSP's
to generate DTMF and modem negotiating tones, to receive and understand
DTMF and modem neg. tones, and to separate the various narrow frequency
bands that make up the communications channels in both directions used to
pass digital information.

A lot of these same modems' DSP's also are capable of the wide spectrum
(relatively) bidirectional streaming of regular audio.  Evidently my modem
is one of these, as the manufacturer included software that utilizes it
to act as an audio in-and-out device.

Since my modem is not unusual, and since there are several pieces of
software in the MS-Windows world that do this function and work with my
modem, and knowing that advanced state of Linux today, I thought for sure
that there was software in Linux to do it as well.

I am unsure if my modem is one of those "winmodems" that uses the host's
CPU to act as a DSP to process the signals.  If so, the likelihood of
software to do this in Linux may even be more readily available.  My other
box is running a winmodem and works just fine with my Debian-based 2.6
kernel as a regular modem.

--
Scott G. Hall
Raleigh, NC, USA
ScottGHall at BellSouth.Net