Download MIL-STD-187

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MIL-STD-187-31O
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c.
(1)
The message must possess a SOM character.
(2)
There must be at least six characters received (otherwise,
the received message is probably an acknowledgment) .
(3)
The message number field (assumed to be the third and fourth
characters of the message) must not contain “parity error”
characters.
A glare situation may occur when two switches connected by an
interswit ch trunk group seize the same trunk simultaneously.
In order to accommodate this situation, one of the two switches
at the ends of everv
--- simalinb! trunk should be classmarked to
“accept glare. ”
6.4.2 .1.7.6 Call Incomplete Messages. A call incomplete message shall
be returned in resuonse to a received CALL INITIATE when any of a
number of condit io& is encountered which makes the completion of the
call impossible. In these cases, the appropriate call incomplete
message shall be returned in place of the CALL COMPLETE message.
six
call incomplete messages (Figure 6.4.5) shall be used: CALLED PARTY
UNAVAILABLE , ALL TRuNKS BUSY, EQUIPMENT BUSY, UNASSIGNED LOOP, INCOMPATIBLE CONNECTION, and INVALID ROUTE.
●
A terminating switch wil 1 return CALLED PARTY UNAVAILABLE when it
determines that the called party is busy on a call of equal or higher
precedence. When CALLED PARTY UNAVAILABLE is received at any switch
In the call, all reserved matrix paths and common equipment will be
released and the copy of the CALL INITIATE awaiting completion shall be
destroyed. When received at the originating switch, the calling’ party
will be sent line busy tone.
An ALL TRUNKS BUSY message will be returned by a circuit switch
to which routing control has not been spilled forward when that switch
determines that :itcannot route the call becauae all trunks are busy
on calls of equa:Lor higher precedence. When a switch receives’ALL’
TRUNKS BuSY, it will attempt to perform alternate routing uSing the
copy of the relevant CALL INITIATE message.
EQUIPMENT BUSY will be returned by the terminating switch when the
called party is ‘idleor preempt ible but the equipment necessary to
‘
effeet a connect:Lon (matrix path, AID conversion equipment, etc. ) is
not. EQUIPMENT BUSY is sent only when the necessary equipment does
exist at the switch, but is simply unavailable. EQUIPMENT BUSY w il1 be
processed at other switches exactly as CALLED PARTY UNAVAILABLE, except
that trunk busy will be sent rather than line busy.
6-4-19
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