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MH88632

Preliminary Information

37

FL

Forward Loop Detect (Output). In the on hook state, a logic low output indicates that

forward loop battery is present. In the off-hook state, a logic low output indicates that

forward loop current is present. Forward loop refers to the Ring Lead negative with respect

to the Tip lead.

38

RG

Ring Lead Ground Detect (Output). A logic low indicates that the Ring lead is at ground

(AGND) potential.

39

VEE

Negative Supply Voltage. -5V dc.

40

VDD

Positive Supply Voltage. +5V dc.

Pin Description (Continued)

Pin #

Name

Description

Functional Description

The MH88632 is a COIC (Central Office Interface

Circuit) used to interface to Central Office 2-Wire

Analog Trunks. The COIC provides both Loop start

and Ground start interface capabilities.

Approvals

FCC part 68, DOC CS-03, UL 1459, CAN/CSA 22.2

No.225-M90 are all system (i.e., connectors, power

supply,

cabinet,

etc.)

requirements.

Since

the

MH88632 is a component and not a system, it

cannot be approved as a stand alone part by these

standards bodies. However, when installed into a

properly designed system, the MH88632 has been

designed

to

meet

the

CO

Trunk

Interface

requirements of FCC, DOC, UL and CSA, and thus

enabling the complete system to be approved by

these standards bodies.

To meet the regulatory high voltage requirements, an

external protection circuit is required. The protection

circuit shown in Figure 9 is matched to the MH88632

and ensures than they meet the high voltage

requirements of FCC, DOC, CSA and UL when

installed in a properly designed system.

Products are designed in accordance with meeting

the above requirements; however, full conformance

to these standards is dependent upon the application

in which the hybrid is being used, and therefore,

approvals are the responsibility of the customer and

Mitel will not have tested the product to meet the

above standards.

DC Loop Termination

The DC loop termination circuitry provides the loop

with an active Dc load termination when a logic low is

applied to the LRC (Loop Start Relay Control) input.

the termination is similar to a DC resistance between

200

Ω and 275Ω. An external relay is used to activate

internal circuitry which switches the termination in

and out of the loop. This is used for both seizing the

line as well as generating dial pulses.

Supervision Features

The supervision circuitry provides the signalling

status outputs. The system controlling the COIC,

monitors

these

logic

outputs.

The

supervision

circuitry is capable of detecting ringing voltage, both

forward and reverse loop battery and loop current,

and both grounded tip lead and grounded ring lead.

a) Supervision Features RV (Ring Voltage

Detect Output)

The RV (Ringing Voltage Detect) output provides a

logic low when ringing voltage is detected. This

detector includes a ringing filter which ensures that

the output toggles at the ringing cadence and not at

the ringing frequency. Typically, this output goes low

50ms after ringing voltage is applied and remains

low for 50ms after ringing voltage is removed.

b) Supervision Features FL & RL (Forward Loop

and Reverse Loop Detect Output).

The FL (Forward Loop Detect) output provides a logic

low when either forward loop battery or forward loop

current is detected (ring lead voltage negative with

respect to ring lead). The RL (Reverse Loop Detect)

output provides a logic low when either reverse loop

battery or reverse loop current is detected (tip lead

voltage negative with respect to ring lead).

See Table 5 for Loop Battery and Current Status

Outputs.