Channel Type 



Modulation Rate 



Coding 



Error Control 



Block Length 



Block Check 

 Character 



full duplex; half-duplex protocol 



0-9600 baud; 2400 baud nominal 



ASCII, odd parity, nontransparent 



block transmission; alternating ack 0, 

 ack 1 



190 data characters maximum and 3 (or 4) 

 framing characters 



user option of Longitudinal 



Redundancy Check (LRC) or Cyclic 

 Redundancy Check (CRC-16) 



Because the full-time circuits are permanent connections, the CDF 

 knows which user is associated with each, and there is no need for 

 identification procedures. If any platforms have emergency 

 transmission capability, the CDF may identify such transmissions 

 with a special header (optional) and data description in the 

 disseminated data bulletin. ^ Operator intervention is not required 

 for routine or emergency data dissemination over a full-time 

 dedicated circuit. 



The bulletin format used contains the following information sequence: 



0) 



o 



6 



+-> 

 +-> 





0) 



0) 



^ 



Function 



Control character (SOH); start of heading 



3-digit message sequence number 



Catalog number; identification of user 



Control character (STX); start of text 



6-digit data description; user constant 



Space character 



2-digits each; day of month, hour, minute of 

 dissemination 



DUP; Space, indicates possibly duplicate bulletin 



End-of-line; carriage return, linefeed 



Number of 

 Characters 



1 



3 



5 



1 

 6 



1 



4 (Optional) 

 2 



^Reference: User Interface Manual, 



22 - 



