|(Scratching head a bit...) I did BE project in communication and hence come
|to know that the telephone ring used in all exchanges is 75V AC RMS, riding
|on -48V DC, to facilitate dialing from ringer (mechanical spring dialing,
|old style) fones.
|
|Now internal modem derives power from PC power supply only. Given the
|reputaion of indian government service, how safe internal modems are, from
|passing the surge to the Mobo?
|
|There are protective circuits etc. on modem but mobo power line directly
|connected to exchange one is rather hairy scene to me. Especially when
|polarity reversal is not impossible with exchange(Happens with electricity
|board too...)
All modems have varistor which protects the circuit from the surges, in
addition to isolation transformer which isolates the telephone line and
internal circuit.
The biggest drawback of internal modem is lack of controller which puts
extra load on processor. External modem will definitely out perform internal
modem on mmx CPU.
Incidentally internal modem does not work on non mmx CPU even in windows,
where as external modem works on any hardware which has a serial port.
Regards,
Mukund Deshmukh
Beta Computronics Pvt. Ltd.
Web Site - www.betacomp.com
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