Figure 18: Analog 4We&M Signaling Types - Juniper CTP2000 Series Hardware Documentation

CTP2000 Hardware Documentation
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Figure 18: Analog 4WE&M Signaling Types
Type I uses two leads—the E and M leads—for signaling. During inactivity, the E lead is
open and the M-lead is connected to ground. The CTP device connects the E lead to a
grounding point to signal off-hook, and the PBX connects the M lead to the battery (–48
V) to signal off-hook. Note that two signaling units cannot be connected back-to-back.
With type I signaling, the signaling and trunk units must be connected by means of a
common ground. Because the two sides are not isolated, they are susceptible to noise
in the audio channels.
Type II uses four leads—E, SG, M, and SB—for signaling. During inactivity, both the E and
M leads are open. To signal off-hook, the PBX connects the M lead to SB and the CTP
device connects the E lead to SG. Note that two signaling units can be connected
back-to-back if the appropriate signaling leads are swapped. With Type II signaling, the
signaling unit and the trunk do not share a common ground.
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