If at any time the user enters STOP, the CDF sends an EOT 

 and goes on-hook. If the user hangs up without answering 

 STOP, the CDF will assume that the previously transmitted 

 data were successfully disseminated . 



(9) If the user disconnects the circuit prior to 



transmission of all the messages, then the CDF considers 

 that no messages have been disseminated . 



(10) Data transmitted on these circuits have all erroneous 

 characters (containing parity errors) replaced with a 

 dollar sign ($). 



(11) If the CDF receives STX CAN ETX LRC from the terminal, 

 signifying a playback error (cassette I/O error), it 

 will send the following message to the user: 



PLAYBACK ERROR. TRY AGAIN. 



The user will be able to reenter his request. 



2.5.3.4 110-Baud DDD Circuit 



The third class of circuit (110 baud dial-up) has the following 

 characteristics : 



Modem : AT&T Model 103A3 



Channel Type : DDD subscriber lines; half-duplex 



Modulation Rate: 110 baud (10 characters/s) 



Coding : Asynchronous ASCII (11 bits) even parity 



Error Control None 



The CDF assumes that the terminal on a 110-baud dialup line is 

 similar to a Teletype Model ASR-33. User communications over these 

 low-speed lines require the following procedures: 



Procedures on 110-baud Line 



(1) Utilizing a terminal, the user dials the telephone 

 number for the 110-baud line. 



(2) The CDF automatically answers, and transmits the 

 message : 



DCS. ENTER ID 



followed by the protocol character WRU (ENQ) 



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