network1
L 0
T DB170.DBW 120
SET
SAVE
CLR
A BR
R #M_DEF
R "TP270_DATA".EV_ACQ
R "TP270_M_EVT".MESSAGE_150
network2
A "TP270_DATA".ALARME_EC
AN #M_DEF
= "TP270_M_EVT".MESSAGE_1
S "TP270_DATA".CLR
S #M_DEF
network3
A(
O "STP662"
O "STP663"
ON "TMST"
)
AN #M_DEF
= "TP270_M_EVT".MESSAGE_21
S "TP270_DATA".CLO
S "TP270_DATA".CLIG_O
S #M_DEF
network4
A "SC1S1"
= L 1.0
A L 1.0
AN #M_DEF
= "TP270_M_EVT".MESSAGE_250
S "TP270_DATA".CLR
S #M_DEF
A L 1.0
BLD 102
= "TP270_LOCALISATION".LOC_250

问下network1、network2的具体作用是什么？其中#M_DEF是什么意思？？
为什么network3、network4中都有对#M_DEF置位的语句呢？很糊涂，这是个什么样的用法？如何触类旁通？