[Asterisk-Users] OT: PRI costs in US

[Steven Critchfield]

On Sun, 2003-03-02 at 21:30, Jon Pounder wrote:
> I am still not really clear why the isdn modems that seem so common 
> can't/won't work in this situation. Is it simply an issue of software does 
> not exist ? Does the modem do something other than simply dump the 
> composite digital datastream into the serial port ? I am familar with how a 
> channelized T1 can be output/input via a v35 HSSI port - Does this same 
> concept not extend to the BRI isdn and a regular speed serial port ? Is the 
> issue that a conventional serial port is topped out at 115k and bri would 
> be 64+64+16 ? If so, how does the modem work in bonded bearer channel mode 
> for data ?

A isdn modem dumps the data to the serial port. Since the 16k channel is
signalling data it is only of interest to the modem. Also there is
serial cards capable of doing 115K, 230K, and 460K speeds. The last ISDN
modem I bought was from Cardinal, and it supported up to 460K serial
speeds, and I bought a SiG 16650 Uart serial card that supported up to
460K serial. For whatever reason the Cardinal modem dies shortly after
getting that speed out of it. Also my provider gave 300 hours a month,
but it was billed by the B channel used so I either had 150 hours bonded
or 300 hours unbonded. Also the ISDN modems I used all used a form of
the Hayes AT command set which would end up limiting them to the same
problems that a standard modem has.

I believe if you look at the list you will find quite a few people in
europe doing ISDN in asterisk, but they are using cards that terminate
ISDN and not external units. The difference is that they sit on the bus,
and don't have to make a serial Uart that is rate limited, nor limited
in how you communicate with it. 

-- 
Steven Critchfield <critch at basesys.com>