Mitel SX-200 EL, Technician'S Handbook

Page: 84 / 262

Technician’s Handbook
74
Test/Verify (Ground Start)
Verify the far-end (CO) circuits by using a standard telephone for
incoming calls. Verify outgoing calls by using a Butt Set with a ground-
start lead (momentarily shorting the ring lead to the ground will produce
a dial tone from the far end).
Verify the near-end (PBX Ground Start) circuits by connecting to known
working far end Ground Start circuits.
Verify that appropriate voltages are present on Tip-Ring in each call
state.
During off-hook condition, 18 mA DC minimum should be drawn from
the CO (typical 35-40 mA).
Tip-Ring is polarity sensitive. PBX will be unable to initiate calls if
reversed. Reverse polarity to verify.
Stop Dial -
-
Receipt of Digits Audible Tones - Busy,
Reorder, Ringback dependent
upon digits dialed and called
party condition
-
Answer
Supervision CO reverses current flow in
Tip-Ring
Disconnect
Supervision Near-end: PBX opens loop
Far-end: CO removes ground
from ring Near or Far-end
termination: Loop
Current is broken
Table 7: Ground Start Trunk Summary (Continued)
Signal
Ground Start Trunk PBX
Outgoing
Ground Start Trunk
PBX Incoming
(Sheet 2 of 2)