Mitel 50005070 Instruction Manual download pdf (Page 262)

100

101

252

SX-200 ICP MX Technician’s Handbook

Test/Verify (Loop Start)

• Verify far-end (CO) circuits by using a standard telephone set in place

of the Loop Start trunk circuit.

• Verify near-end (PBX Loop Start) circuits by connecting to a local PBX

ONS circuit.

• Check for appropriate voltages on Tip-Ring in each call state.

• During off-hook condition, 18 mA DC minimum should be drawn from

the CO (typical 25-40 mA).

• Some Key/PBX systems may be polarity sensitive; reverse Tip-Ring to

verify.

Table 51: Loop Start Line/Trunk Summary

Signal

Loop Start Line PBX

Outgoing

Loop Start Line PBX

Incoming

Seize Tip-Ring leads activated

(shorted); Loop Current flows

in line

90Vac is applied to Ring

lead in 2 sec on, 4 sec

off cadence

Seize

Acknowledgment

Loop Current and/or dial tone

generated

—

Digits Loop Current toggled (Rotary)

or DTMF

—

Stop Dial — —

Receipt of Digits Audible Tones - Busy,

Reorder, Ringback dependent

upon digits dialed and called

party condition

—

Answer Supervision Some COs can reverse

current flow

Tip-Ring leads activated

(shorted); Loop Current

flows in line

Disconnect

Supervision

Near- end termination: PBX/

Telephone can break Loop

Current

Near- end termination:

PBX/Telephone can

break Loop Current

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