stored in the appropriate user's area of the data output buffer to 

 await dissemination. The preferred method of dissemination is in 

 real time over a dedicated communication channel assigned to the 

 user. Alternative arrangements, such as dissemination over dialup 

 circuits, may also be used. 



1.2.8 How Is the DCS Operation Controlled? 



DCS operation is controlled by the Data Processing Subsystem computer 

 which handles the routine functions of message scheduling, status 

 reporting, data reception, buffering, and dissemination. Manual 

 operator intervention is provided for startup procedures. 



Control of the DCS is exercised by comparison of real-time system 

 activity to the system schedule stored in the computer. Messages 

 are periodically sent by the computer to the CDA subsystem which 

 include platform address identifiers scheduled for activity, channel 

 occupation, and time of report, and whether the reporting platform 

 is self-timed or requires interrogation. The CDA equipment receives 

 the platform sensor data transmitted through the satellite transponder, 

 performs character error checks, and temporarily stores the data. 

 The received messages are checked at the CDA for expected address 

 identifiers and transmitted to the World Weather Building Central 

 Distribution Facility (CDF), along with all pertinent error information. 

 If a scheduled message was not received at the expected time, the CDF 

 computer notifies the user. The occurrence of an unexpected 

 (unscheduled) platform message is analyzed by the computer to determine 

 whether it was due to an equipment malfunction, platform site trans- 

 mitter test, or emergency condition, with appropriate action 

 automatically being taken and abnormal status indication provided to 

 the user. 



Received sensor platform messages and abnormal response messages are 

 formatted into bulletins in the CDF data buffer. Dissemination of 

 these bulletins to users will be attempted in real time, as the data 

 replies are received, over the dedicated circuit assigned to the user. 

 Reformatting of platform response data is not performed; these data 

 appear unmodified in the bulletins disseminated to the users. Users 

 must consider the effect of their platform sensor data format on their 

 data terminal, e.g.: 



(1) Requirements for carriage return, line feed, and 

 characters needed for proper display. 



(2) Compatibility of the terminal character set with the 

 transmitted characters. 



(3) Use of characters or character sequences for special 

 purposes. 



- 7 - 



