MH88614 Просмотр технического описания (PDF) - Mitel Networks
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MH88614 Datasheet PDF : 10 Pages
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Advance Information
MH88614
Pin Description- (Continued)
Pin # Name
Description
19
IC Internal Connection
20
VX Transmit (Output). The audio output signal appears on this pin and is internally a.c.
coupled. This signal is applied to the programmable CODEC.
21
IC Internal Connection
22
LCA Loop Current Adjust (input). The circuit has two constant current settings that are logic
selectable
23
IC Internal Connection
24
LA Loop Alarm (Output) When the loop impedance exceeds the maximum limits that the SLIC
can support for a specified voltage & current this output will go low. This indicates that the
SLIC will no longer support the line. Note: This pin will also pulse low if Loop Disconnect
Dialling is performed, and goes low when the phone is on hook.
25
IC Internal Connection
26 VRING Ring Voltage Supply. This pin is the supply for the Ringing signal to the telephone.
(Typically 90VRMS on -48V battery).
27
VMSE Message Voltage Supply. This pin is the supply for the message signal to the telephone.
(Typically -100V)
28
RE Ring Enable (Input). The ringing signal is applied across Tip & Ring by applying a logic 1 to
this pin while the phone is “On Hook”. Ringing will be automatically stopped when the
phone goes “Off Hook” regardless of the state of the RE pin.
29
MSE Message Signal Enable (Input). A cadenced signal can be applied to this pin which will
switch the VMSG voltage onto Tip & Ring. The output voltage is internally conditioned to
prevent bell tinkle on the telephone. This is automatically switched off when the phone goes
off hook.
30
SHK Switch Hook (Output). The output of this pin goes low when the phone goes “Off Hook”
and can be used externally to switch MSE off.
Functional Description
Loop Supervision
The MH88614 is an ONS SLIC for use with a
programmable / intelligent CODEC or DSP. The SLIC
performs all of the normal interface functions
between the CODEC and the analog telephone set
whilst having such additional features as Earth
Ground Button Detection, message switching and
Ringing switching with zero crossing.
The MH88614 is available as a 30 pin SIL package
to increase board densities.
2 Wire to 4 Wire Conversion
The hybrid performs 2 wire to 4 wire conversion by
taking the 4 wire signal from the programmable
CODEC at VR and converting it to a 2 wire
differential signal at Tip & Ring. The 2 wire signal
applied across Tip & Ring by the phone is converted
to 4 wire signal at Vx which is the output from the
SLIC to the programmable CODEC. Both the VR
input & Vx output are internally a.c. coupled.
The Loop Supervision circuit monitors the state of
the phone line and provides three different output
stages.
When the phone goes “Off Hook” the SHK pin goes
low to indicate this state. This pin reverts to a high
state when the phone goes back “On Hook” (see
figure 3).
When the phone is off hook the circuitry can also
detect two other features of the line status namely
Earth Ground Button & Loop Alarm.
A logic low signal on the Earth Ground Button output
indicates that an earth ground path has been applied
to the Tip or Ring lead of the telephone. This function
can be used for recall operations on phone sets with
Earth Ground Buttons.
The Loop Alarm signal low to indicate that the RLoop
has been exceeded and that the circuit will no longer
support the line.
2-131
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