MH88622 datasheet(8/10 Pages) MITEL

8 / 10 page

2-180

MH88622

Preliminary Information

Figure 4 - Typical Protection Circuit

PROTECTION

PTC

RESISTOR

5 Ohms

TISP2290

P2702AB

PTC

RESISTOR

5 Ohms

Off-Hook and Dial Pulse Detection

The SHK pin goes low when e DC loop current

exceeds a specified level. The threshold level is

internally set by the bias voltage of the switch hook

detect circuit.

Dial

pulse

can be detected by monitoring

the

interruption rate at the SHK pin. These dial pulses may

need to be debounced by the systems software.

Ring Trip Detection

The interface permits detection of an Off-Hook

condition during ringing. If the subscriber set goes

Off-Hook when the ringing signal has been applied,

the DC loop current flow will be detected within

approx. 100msecs and the SHK output will go low.

The ringing is automatically disabled by the internal

hardware.

Longitudinal Balance

Precision laser trimming of resistors in the hybrids

ensures good overall longitudinal balance.

The interface circuitry can operate in the presence of

induced longitudinal currents of up to 40mA rms at

60Hz.

High Voltage Capability

Inherent in the thick film process is the ability of the

thick film process dielectric strengths of greater than

1000 VAC or 1500 VDC. The thick film process

allows

easy

integration

surface

mount

components such as the high voltage bi-polar power

transistor line drivers. This allows for simpler, less

elaborate and less expensive protection circuitry

required to handle high voltage transients and fault

conditions caused by lightening, induced voltages

and power line crossing.

On Hook Transmission

The MH88622 provides for on-hook transmission

which supports features such as Automatic Number

identifications (ANI).

Loop Length

The MH88622 can accommodate loop length of up to

2000

Ω

minimum

(including

the

subscriber

equipment).

MH88622 Datasheet(PDF) 8 Page - Mitel Networks Corporation

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