Comtech EF Data MIDAS 4 System and Design - Manual (Page 54)

System and Design Manual, Revision 2
3–12
Theory of Operation
The sequence is illustrated in Figure 3-2.
CALLING NODE NMS CALLED NODE
CIRCUIT ASSIGNMENT CIRCUIT ASSIGNMENT
STATUS (OK)
CONFIGURE TRAFFIC
MODEM AND TURN
M
AND RECEIVE ON ODEM TRANSMIT
CONFIGURE TRAFFIC
MODEM AND TURN
M
AND RECEIVE ON ODEM TRANSMIT
TRAFFIC MODEM
LOCKS
CIRCUIT REQUEST
REQUEST FOR A
DATA CIRCUIT VIA
THE USER PORT
TRAFFIC MODEM
LOCKS
STATUS (OK)
Figure 3-2. User-Initiated Circuit Setup
The video circuit setup is similar to that of the data circuit.
Circuit Termination
A data or video circuit termination could be initiated by:
• The MIDAS Controller, in response to operator action
• The traffic node, due to the following:
♦ User port command
♦ RTS/DTR goes inactive
♦ Traffic modem loses lock 4
♦ Call duration expires (for a scheduled circuit)
♦ (For CiM Modems only) - Absence of IP packets destined for a
satellite route through the duration of the user configurable timeout
period.
4 The time from the modem losing lock to circuit termination is configurable.