' , , ' , . - .
(BBS Bulletin Board System), , , "on-line" (, ).
, , FidoNet Inter- net/Relcom/UANet. ϳ , , .
' , , . , , "". , ' ( ), , . .
, . , FSK (Frequency Shift Keying ) 300 ( , 1 /) PSK (Phase Shift Keying ) 2400 .
FSK . 1070 , 1270 . 2025 , 2225 .
PSK : 2400 , 1200 . , . :
0 00;
90 01;
180 10;
270 11.
, (DPSK, QAM, TCM). , , - ' ( RS232 Ѳ V.24), , '. ISA, Ѳ.
( PC- (PCMCIA), ' ""). , '. , , , .