[Asterisk-Users] ADSI phone vs. IP phone

[Andrew Kohlsmith]

> If I read above correctly, you imply that ADSI phones don't need
> wall-warts (A/C power transformers that plug into the wall).  I'd assume
> that based on the sizable LCD screen, potential back-lighting,
> microcontroller(s), etc, that an ADSI phone would have to have a
> wall-wart, especially if you wanted to use any of its functionality while
> it is on-hook.  I have designed a phone or two in my past (many years
> ago) and, as I recall, there is almost *no* current available from the
> telco while a phone is on-hook.  You might be able to trickle-charge a
> very small battery, or run an RCA 1802 processor (microamps), but that's
> about it.

Actually you are guaranteed a 20mA loop from the telco (and I would imagine 
from any channel bank as well) -- with CMOS technology you can do a _lot_ 
with 20mA...  Unfortunately backlighting is not one of them, nor is driving 
a lot of LEDs.  :-)

And yes, I had not seen the forest for the trees and I ran smack into the 
middle of one of them. (I have done this in real life too once...  the 
looks people give you...)  I take back my statement that the wall-warts are 
an IP phone-only thing, this is simply not true.  And IP phones give you 
the option of POE, something that you can't do with ADSI phones.

Regards,
Andrew