2-199

Features

Programmable gain, network balance and
impedance

Transformerless 2-4 wire conversion

Constant current with constant voltage fallback
for long loop capability

Pin compatible with MH88632, MH88620 and
MH88628

Unbalanced detection (Tip, Ring ground
sensing)

Auto ring trip with zero crossing

On-Hook transmission (ANI) capability

Compatible with requirements of CCITT,
DOC/FCC and CSA/UL

Excellent power dissipation (SIL vertical
mounting)

12/16kHz meter pulse injection control

Solid State TIP/RING reversals

Ringing amplifier

Applications

On/Off Premise PBX Line Cards

DID (Direct Inward Dial) Line Cards

Central Office Line Cards

Description

The Mitel MH88628 SLIC provides all of the
functions required to interface 2-wire off premise
subscriber loops to a serial TDM, PCM, switching
network of a modern PBX. The MH88628 is
manufactured using thick-film hybrid technology
which offers high voltage capability, reliability and
high density resulting in significant printed circuit
board area savings. A complete C.O. line card can
be implemented with very few external components.

SHK

N2
NATT

TF2

TF1

TIP

RF2

RF1

RING

LCA

VDD

VRLY

VEE

AGND

Unbalanced

Detection

Decoder

Circuit

Driver

Circuitry

and

Speech

Circuit

Ringing

External

Signal

Input

Loop

Current

Set

Switch-hook

Threshold Set

Switch-hook

Detect

Impedance

Network

Ring

Filter

2-4 Wire

Conversion

Gain Adjust

VBat LGND

Amplifier

RNGD

SEL1 SEL2

ACRI DCRI

ESI

ESE

Z600 Z1

Z900

GRX1 GRX0 RX GTX1 GTX0 TX

Matched

Feed

Resistors

ISSUE 5

April 1995

Ordering Information

MH88628

40 Pin SIL Package

C to 70

Figure 1 - Functional Block Diagram

MH88628

Central Office SLIC

Preliminary Information

2-200

MH88628

Preliminary Information

Figure 2 - Pin Connections

Pin Description

Pin #

Name

Description

TIP

Tip Lead. Connects to the "Tip" lead of subscriber line.

RING

Ring Lead. Connects to the "Ring" lead of the subscriber line.

TF1

Tip Feed 1. Access point for balanced ringing. Normally connects to TF2.

TF2

Tip Feed 2. Access point for balanced ringing. Normally connects to TF1.

RF1

Ring Feed 1. Access point for balanced ringing. Normally connects to RF2.

RF2

Ring Feed 2. Access point for balanced ringing. Normally connects to RF1.

LGND

Battery Ground. VBat return path. Connected to system's energy dumping ground.

LCA

Current Limit Set (Input). The current limit is set by connecting an external resistor to
ground. For 30mA default current, this pin is tied to GND.

VBat

Battery Voltage. Typically -48Vdc is applied to this pin.

DCRI

DC Ringing Voltage Input. A continuous 120Vdc is applied to this input.

RGND

Relay Driver Ground Connection.

VRLY

Relay Supply Voltage Connection.

Ring Drive (Output). Connects to ring relay coil.

SEL1

Select 1 (Input). Refer to Table 5

SEL2

Select 2 (Input). Refer to Table 5.

ESI

External Signal Input. 12/16kHz meter pulse input.

ESE

External Signal Enable. Applies the external signal to the line.

AGND

Analog Ground. VDD and VEE return path.

NATT

Network Balance AT+T Node. Connects to N1 for a network balance impedance of AT&T
compromise (350

+ 1k

// 210nF); the device's input impedance must be set to 600

This node is active only when NS is at logic high. This node should be left open circuit when
not used.

21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40

Z900

Z1
Z2

GTX0
GTX1

GRX0
GRX1

ACRI

Z600

SHK

IC
IC
IC

VEE

VDD

TIP

RING

TF1
TF2

RF1
RF2

LGND

LCA

VBat
DCRI

RGND

VRLY

SEL1
SEL2

ESI

ESE

AGND

NATT

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20

2-201

Preliminary Information

MH88628

Network Balance Node 1(Input). 0.1 times the impedance between pins N1 and N2 must
match the device's input impedance, while 0.1 times the impedance between pins N1 and
AGND is the device's network balance impedance. This node is active only when NS is at
logic high. This node may be terminated when not used (i.e., NS at logic low).

Network Balance Node 2 (Output). See N1 for description.

Z900

Line Impedance 900

Node. Connects to Z1 for a line impedance of 900

. This node

should be left open circuit when not used.

Line Impedance Node 1 (Input). 0.1 times the times the impedance between pins Z1 and
Z2 is the device's line impedance. This node must always be connected.

Line Impedance Node 2 (Output). 0.1 times the times the impedance between pins Z1
and Z2 is the device's line impedance. This node should be left open circuit when not used.

Transmit (Output). 4-Wire (AGND) referenced audio output.

Receive (Input). 4-Wire (AGND) referenced audio input.

GTX0

Transmit Gain Node 0. Connects to GTX1 for 0dB transmit gain.

GTX1

Transmit Gain Node 1. A resistor to AGND provides transmit gain adjustment.

GRX0

Receive Gain Node 0. Connects to GRX1 for 0dB gain.

GRX1

Receive Gain Node 1. A resistor to AGND provides receive gain adjustment.

ACRI

AC Ringing Voltage Input. A 1.5Vrms 20Hz signal is applied to this input.

Z600

Line Impedance 600

Node (Output). Connects to Z1 for a line impedance of 600

This pin should be left open circuit when not used.

Network Balance Setting (Input). The logic level at NS selects the network balance
impedance. A logic 0 enables an internal balance equivalent to the input impedance (Z

While a logic 1 enables an external balance 0.1 times the impedance between pins N1 and
AGND balanced to 0.1 times the impedance between pins N1 and N2. The impedance
between N1 and N2 must be equivalent to 10 times the input impedance (Z

SHK

Off-Hook Indication (Output). A logic low output indicates when the subscriber equipment
has gone Off-Hook.

Unbalance Detect (Output). A log IC low output indicates when the DC current flow in the
Tip and Ring leads is unbalanced, indicating that the subscriber equipment has grounded
the Ring lead.

36,37,38

Internal Connection. These pins are internally connected and must be left open

VEE

Negative Supply Voltage. -5V dc.

VDD

Positive Supply Voltage. +5V dc.

Pin Description (Continued)

Pin #

Name

Description

2-202

MH88628

Preliminary Information

Absolute Maximum Ratings*

* Exceeding these values may cause permanent damage. Functional operation under these conditions is not implied.

Recommended Operating Conditions

* Typical figures are at 25

C with nominal

5V supplies for design aid only.

DC Electrical Characteristics

DC Electrical Characteristics are over recommended operating conditions unless otherwise stated.
* Typical figures are at 25

C with nominal

5V supplies and are for design aid only.

Parameter

Sym

Min

Max

Units

Comments

Supply Voltage

Bat

DCRI

+0.3

-0.3

+0.3

-0.3

-6

140

V
V
V
V

With respect LGND

Storage Temperature

-40

+125

Parameter

Sym

Min

Typ*

Max

Units

Comments

Supply Voltage

Bat

-44

4.75

-4.75

-48

+5.0

-5.0

-60

5.25

-5.25

V
V
V

Operating Temperature

AC Ring Generator

Voltage

Frequency

Vrms

DCRI

Input DC Voltage

DCRI

110

120

130

Vdc

Characteristics

Sym

Min

Typ*

Max

Units

Test Conditions

Operating Loop Current

Var in loop current from nominal

Loop

mA
mA
mA
mA

Loop

2300

VBat =-48V

Loop

, LCA -

GND

Operating Currents

Bat

25
25

mA
mA

Loop

=0 (off Hook),

LCA=GND
R

Loop

= open (On-

Hook)
On-hook or Off-Hook
On-Hook or Off-Hook

Power Dissipation

300

Active
Standby/Idle

SHK

Low level Output Voltage
High Level Output Voltage

3.7

0.5

V
V

= 400

= 40

SEL1
SEL2

ESE

Low Level Input Voltage
High Level Input Voltage

2.4

0.8

V
V

High Level Input Current
Low Level Input Current

20
20

=5.0V

=0.0V

2-203

Preliminary Information

MH88628

AC Electrical Characteristics

* Typical figure are at 25

C with nominal

5V supplies and are for design aid only.

AC Electrical Characteristics are over recommended operating conditions unless otherwise stated.

Notes:
Impedance set by external network of 600

or 900

default.

External network for test purposes consists of 2200

+ 8200

// 11.5nF between pins Z1 and Z2, the equivalent Zin has 1/10

the impedance

and is equivalent o 220

+820

// 115nF.

Test condition uses a Zin value of 600

, 900

and the above external network.

Test conditions use a transmit and receive gain set to 0dB default and a Zin value of 600

unless otherwise stated.

"Ref" indicates reference impedance which is equivalent to the termination impedance.
"Net" indicates network balance impedance.
Refer to Table 1, 2 for TX, RX gain adjustment.

Characteristics

Sym

Min

Typ*

Max

Units

Test Conditions

TX Gain

externally adjustable

RX Gain

externally adjustable

Ringing Capability

REN

On-Hook Transmission
Signal Input Level
Gain 6

2.0

rms

Bat

=-48V

T-R load = 10k

min.

External Signal Output Level

1.75

2.25

rms

Bat

= -48V, T-R load=

200

LCA=0V, Zo-600

Gain=0dB

SHK Rise Time
Fall time

1
1

ms
ms

Dial Pulse Detection

2-Wire Termination
Impedance

600/

900

Selectable

Off-Hook Detect Threshold

2-Wire Return Loss

20
20
20

dB
dB
dB

300 to 500Hz
500 to 2500Hz
2500 to 3400Hz

Longitudinal Balance

Longitundinal to Metallic

58
53

dB
dB

200-1000Hz
1kHz - 3k4Hz

Longitudinal Current
Capability

20mA per lead

Idle channel Noise

Rx to T-R

T-R to Tx

dBrnC
dBrnC

Transhybrid Loss

THL

200-3400Hz

Unbalanced Detect Threshold

Analog Signal Overload Level
At Tip and Ring

dBm

T-R=600

, V

Bat

=-48V

Ringing Signal Voltage

Vrms

Ringing Frequency

Ring Trip Delay

100

Absolute Gain, Variation

+0.1

0dB at T-R, 1kHz

Relative Gain, reference to
1kHz

+0.05

300-3400Hz

Power Supply Rejection Ratio

Bat

PSRR

24
24
24

1kHz, 100mVpp

MH88628

Preliminary Information

2-204

Functional Description

The SLIC uses a transformerless electronic 2-wire to
4-wire conversion which can be connected to a
Codec to interface the 2 wire subscriber loops to a
time division multiplexed (TDM) pulse code
modulated (PCM) digital switching network. For
analog applications, the Tx and Rx of the 2-4 wire
converter can be connected directly to an analog
crosspoint switch such as the MT8816. Powering of
the line is provided through precision battery feed
resistors. The MH88628 also contains control,
signalling and status circuitry which combines to
provide a complete functional solution which
simplifies the manufacture of line cards. This
circuitry is illustrated in the functional block diagram
in Fig. 1. The MH88628 is designed to be pin
compatible with Mitel's MH88632 and MH88625.
This allows a common PCB design with common
gain, input impedance and network balance.

Approvals

FCC part 68, CCITT, DOC CS-03, UL 1459, CAN/
CSA 22.2 No.225-M90 and ANSI/EIA/TIA-464-A are
system level safety standards and performance
requirements. As a component of a system, the
MH88628 is designed to comply with the applicable
requirements of these specifications.

Battery Feed

The loop current for the subscriber equipment is
sourced through a pair of matched 200

resistors

connected to the Tip and Ring. The two wire loop is
biased such that the Ring lead is 2V above VBat
(typically -46V) and the Tip lead is 2V below LPGD
(typically -2V) during constant voltage, constant
current mode.

The SLIC is designed for a nominal battery voltage
of -48Vdc and can provide the maximum loop current
of 45mA under the condition.

The MH88628 is designed to operate down to a
minimum of 16mA dc, with a battery voltage of -44V.
The Tip and Ring output drivers can operate within
2V of V

Bat

and LGND rails. This permits a maximum

loop range of 2300

Loop Current Setting

The MH88628 SLIC is a constant current with
constant voltage fallback design. This design feature
provides for long loop capability regardless of the
constant current setting. Refer to Graph 1.

The LCA (Loop Current Adjust) pin is an input to an
internal resistor divider network which generates a
bias voltage. The loop current is proportional to this
voltage. The loop current can be set between 20 and
45mA by various connections to the LCA pin as
illustrated in Table 5 and Figure 8. The loop current
during a fault condition will be limited to a safe level.
Primary over-current protection is inherent in the
current limiting feature of the 200

battery feed

resistors. Refer to Graph 1.

Receive and Transmit Audio Path

The audio signal of the 2-wire side is sensed
differentially across the external 200

feed resistors

and is passed on to a second differential amplifier
stage in the 2W/4W conversion block. This block
sets the transmit gain on the 4-wire side and cancels
signals originating from the receive input before
outputting the signal.

Programmable Transmit and Receive
Gain

Transmit Gain (Tip-Ring to Tx) and Receive Gain (Rx
to Tip-Ring) are programmed by connecting external
resistors (RRX and RRT) from GRXI to AGND and
from GTX1 to AGND as indicated in Figure 3 and
Tables 1 and 2. The programmable gain range is
from -12dB to +6dB; this wide range will
accommodate any loss plan. Alternatively, the
default Receive Gain of 0dB and Transmit Gain of
0dB can be obtained by connecting GRX0 to GRX1
and GTX0 to GTX1. In addition, a Receive gain of
+6dB and Transmit Gain of +6dB can be obtained by
not connecting resistors RRX and RTX. For correct
gain programming, the MH88628's Tip-Ring
impedance (Z

) must match the line termination

impedance.

For optimum performance, resistor RRX should be
physically located as close as possible to the GRX1
input pin, and resistor RTX should be physically
located as close as possible to the GTX1 input pin.

2-205

Preliminary Information

MH88628

Constant

Current Region

Constant

Voltage

Region

Loop

(

)

Loop

(mA)

Graph 1 - ILoop/RLoop Characteristics

Two wire Port Termination Impedance

The AC termination impedance of 600 or 900

, of

the 2W port, is set using active feedback paths to
give the desired relationship between the line
voltage and the line current. The loop current is
sensed differentially across the two feed resistors
and converted to a single ended signal. This signal is
fed back to the Tip/Ring driver circuitry such that
impedance in the feedback path gets reflected to the
two wire port. The MH88628's Tip-Ring impedance
(Z

) can be set to 600

, 900

or to a user

selectable value. Thus, Z

can be set to any

international requirement. The connection to Z1
determines the input impedance. With Z1 connected
to Z600, the line impedance is set to 600

. With Z1

connected to Z900, the line impedance is set to
900

. A user defined impedance can be selected

which is 0.1 times the impedance between Z1 and
Z2.

For example, with 2200

in series with 11.5nF in

parallel with 8200

, all between Z1 and Z2, the

devices line impedance will be 220

in series with

115nF in parallel with 820

. See Table 3 and Figures

4 & 5.

Network Balance

Transhybrid loss is maximized when the line
termination impedance and SLIC network balance
are matched. The MH88628's network balance
impedance set can be set to Zin, AT&T (350

+ 1k

//210nF) or to a user selectable value. Thus, the
network balance impedance can be set to any
international requirement, A logic level control input
NS selects the balance mode. With NS at logic low,
an internal network balance impedance is matched
to the line impedance (Z

). With NS at logic high, a

user defined network balance impedance is selected
which is 0.1 times the impedance between N1 and
AGND. For example, with 2200

in series with

11.5nF in parallel with 8200

, all between N1 and

AGND, and NS at logic high, the devices network
balance impedance is 220

in series with 115nF in

parallel with 820

; the impedance between N1 and

N2 must be equivalent to 10 times the input
impedance (Z

). In addition, with NS at logic high, an

AT&T network balance impedance can be selected
by connecting NATT to N1; in this case, no additional
network is required between N1 and N2. See Table 4
and Figure 6.

12/16kHz Meter Pulse

The MH88628 provides control of an external signal
path to the driver. A 12/16kHz continuous signal can
be applied to the ESI pin. Control of the ESE input
allows the metering signal to be transmitted to the
line.

Unbalanced Detection

The Unbalanced Detect (UD) pin goes low when the
DC current through the two battery feed resistors is
unbalanced i.e., when the average DC current into
the Ring lead exceeds the current flow out of the Tip
lead (indicating that the Ring lead has been
grounded).

When the SLIC is interfaced to ground start
subscriber equipment during the idle state, the UD
output is monitored for indication of the subscribers
Ring Ground signal. The maximum loop current
supplied by the feed circuitry under this condition is
limited.

2-206

MH88628

Preliminary Information

MH88628

10k

GRX0

GRX1

GTX0

GTX1

RRX

RTX

Transmit Gain

(Tip-Ring to Tx)

AV= -20log 0.5 + 5k

RTX

RTX = 5k

(-AV/20)

-0.5

Example

RTX=38k

; AV= +4dBV

Receive Gain:

(RX to Tip-Ring)

RRX = 5k

(-AV/20)

-0.5

Example:

RRX=4.6k

; AV= -4dBV

[

]

AV= -20log 0.5 + 5k

RRX

[

]

Ring Trip Detection

The interface permits detection of an Off-Hook
condition during the 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 ring relay is automatically disabled by the
internal hardware.

Control Decode

The different modes of operation are selected by
decoding the SEL1 and SEL2 inputs (see Table 5).

DTMF

The DTMF tones are transmitted and received at the
4-wire port.

Figure 3 - Gain Programming with External Components

Longitudinal Balance

The longitudinal balance specifies the degree of
common mode rejection in the 2 to 4 wire direction.
Precision laser trimming of internal resistors in the
hybrid ensures good overall longitudinal balance.

The interface circuitry can operate in the presence of
induced longitudinal currents of up to 40mA at 60Hz.

Off-Hook and Dial Pulse Detection

The SHK pin goes low when the DC-loop current
exceeds a specified level. The threshold level is
internally set by the bias voltage of the switch-hook
detect circuitry. Dial pulse can be detected by
monitoring the interruption rate at the SHK pin.
These dial pulses would be debounced by the
system's software.

2-207

Preliminary Information

MH88628

Z900

Z600

Z900

Z600

Input impedance (Z

) set to 600

Input Impedance (Z

) set to 900

Note: Make connection between Z1 and other points as short as possible

MH88628

Z900

Z600

Notes:

1) The 10xZ

network must be set to 10 x the desired input impedance (Z

2) The network balance must be set to the desired network balance. See
section on network balance.

3) Make connection between Z1 and component as short as possible.

= 0.1 x

1/RP + (S x CP)

where S = j x w

and w = 2 x

x f

Example:

If RS = 2200

RP = 8200

, CP= 11.5nf

Then the input impedance (Z

) is 220

series with 820

in parallel with 115nF.

10 x Z

[

]

RS +

Figure 4 - Input Impedance (Z

) Settings with Z

equal to 600 or 900

Figure 5 - Input Impedance (Z

) Settings with Z

not equal to 600 to 900

2-208

MH88628

Preliminary Information

VDD

MH88628

NATT

Network balance is set to the input

Network balance is set to the AT&T compromise

Note: Make connection between Z1 and other points as short as possible

Impedance (Z

)

network (350

+ 1000

// 210nF)

impedance. The input impedance must be
set to 600W.

MH88628

NATT

Notes:

1) The 10xZ

network must be set to 10 x the desired input impedance (Z

2) The network balance must be set to the desired network balance. See
section on network balance.
3) Make connection between Z1 and component as short as possible.

ZNETBAL = 0.1 x

1/RP + (S x CP)

where S = j x w
and w = 2 x

x f

Example:

If RS = 2200

RP = 8200

CP= 11.5nf

Then the network balance impedance

in parallel with 115nF

VDD

10 x Z

10 x

NETBAL

10 x Z

(ZNETBAL) is 220

in series with 820

[

]

RS +

Figure 6 - Network Balance Setting with NETBAL equal to Z

or AT&T

Figure 7 - Network Balance Setting with NETBAL not equal to Z

or AT&T

2-209

Preliminary Information

MH88628

Tables 1 & 2: Transmit and Receive Gain Programming

Note 1: See Figures 3 and 4 for additional details.
Note 2: Overall gain refers to the receive path of PCM to 2-wire, and transmit path of 2-wire to PCM.

Note 1: NA indicates high impedance (10k

) connection to this pin does not effect the resulting network balance.

Note 2: See Figure 4 & 5 for Application Circuits.

Note 1: NA indicates high impedance (10k

) connection to this pin does not effect the resulting network balance.

Note 2: Low indicates Logic Low.
Note 3: See Figures 6 and 7 for Application Circuit.

Transmit

Gain (dB)

RTX Resistor

Value (

)

Notes

+6.0

No Resistor

+4.0

38.3k

Results in 0dB overall gain when used with Mitel A-law codec (i.e.
MT8965)

+3.7

32.4k

Results in 0dB overall gain when used with Mitel

-law codec (i.e.

MT8964)

0.0

GTX0 to GTX1

-3.0

5.49k

-6.0

3.32k

-12.0

1.43k

Receive Gain

(dB)

RRX Resistor

Value (

)

Notes

+6.0

No Resistor

0.0

GRX0 to GRX1

-3.0

5.49k

-3.7

4.87k

Results in 0dB overall gain when used with Mitel A-law codec (i.e.
MT8965)

-4.0

4.64k

Results in 0dB overall gain when used with Mitel

-law codec (i.e.

MT8964)

-6.0

3.32k

-12.0

1.43k

Table 3: Input Impedance Settings

Z600

Z900

Resulting input impedance (Z

)

Connect Z1 to Z600

600

Connect Z1

to Z9000

Connect Z1

to Z900`

900

Connect network from Z1 to Z2

0.1 x impedance between Z1 & Z2

Table 4: Network Balance Settings

NS (Input)

NATT

Resulting input impedance (Z

)

Low

Equivalent to Z

High

Connect N1

to NATT

AT&T compromise (350

+ 1k

// 210nF)

must be 600

High

Connect network from N1 to
AGND equivalent to 10 x
NETBAL. Connect network
from N1 to N2 equivalent to 10
x Zin.

0.1 x impedance between N1 & N2

2-210

MH88628

Preliminary Information

High Voltage capability

Inherent in the thick-film process is the ability of the
substrate to handle high voltage. The standard Mitel
thick-film process provides dielectric strengths of
greater than 1000VAC or 1500VDC. The thick-film
process allows easy integration of surface mount
components such as the high voltage bi-polar power
transistor line drivers. This allows for simplier, less
elaborate and less expensive protection circuitry
required to handle high voltage transients and fault
conditions caused by lightning, induced voltages and
power line crossings.

On-hook Transmission

The MH88628 provides for on-hook transmission
which supports features such as Automatic Numbers
Identification (ANI). The (ANI) information is a FSK
signal originating from and sent by the C.O. during
the off period of the ringing voltage being sent to the
subscribers set. The signal is present during the off
period between the first and second ring. The
subscribers set decodes the FSK signal and displays
the calling party's number.

TIP Disable

A relay driver, controlled by SEL1 and SEL2, is
provided to drive a relay which can be used to
disable the TIP line when the MH88628 is used for a
ground start central office interface.

Loop Length

The MH88628 can accommodate loop length of up to
2300

minimum (including the subscriber

equipment). This corresponds to approximately 8km
using 26AWG twisted pair or 15km using 24AWG
twisted pair.

Central Office Operation

The MH88628 can be configured for ground start
C.O. applications with the addition of Q1, D1 and K2,
as shown in Figure 9. Ground start requires control of
the Tip lead to remove battery ground from
subscriber loop. For loop start applications, control of
the Tip lead is not required.

C.O's perform Tip/Ring reversals to indicate that a
tool call has been dialled. The Tip/ring reversal can
indicate a toll diversion signal.

Internal Ringing Amplifier Operation

The MH88628 offers an on-board ringing amplifier. A
1.5 VRMS, 20Hz signal is amplified internally and
applied to TIP and RING leads in a balanced
configuration. A +120Vdc supply are applied
continuously to the MH88628. The decode signals on
SEL1 and SEL2 enable the ringing signal to the TIP
and RING when required.

Loop Current Setting

Figure 8 - Loop Current Setting

+5V

LCA

-5V

2-212

MH88628

Preliminary Information

Figure 10 - Typical Protection Circuit

Table 5: Control Decode Table

Mode

Condition

SEL1

SEL:2

Normal Operation

Apply internal balanced ringing

Reverse TIP and RING

Enable Relay Driver

Table 6: Loop Current Setting

Loop

Current

Ref. Fig #

LCA Pin Connection

Connect 10k

from LCA to +5V

Connect 22k

from LCA to +5V

Connect 36k

from LCA to +5V

LCA open circuit

Connect 24k

to -5V

Connect 10k

from LCA to -5V

MH88628

PRO1

SUGGESTED COMPONENTS:

F1, F2 1A, 250VAC, SLO-BLOW LITTLEFUSE 230 2AG

R1, R2, 10

, 1000V, 1/2W RESISTOR (FLAME RATED)

PRO1 SOLID STATE TRANSIENT SUPPRESSOR, EG TISP2300L, P2703AB

F1, R1 AND F2, R2 MAY BE FUSIBLE RESISTORS OR PTCs

PRIMARY MDF

PROTECTION

HEAT COIL

GAS TUBE

HEAT COIL

SECONDARY PROTECTION

Ð­Ð»ÐµÐºÑ‚Ñ€Ð¾Ð½Ð½Ñ‹Ð¹ ÐºÐ¾Ð¼Ð¿Ð¾Ð½ÐµÐ½Ñ‚: MH88628

ÐÐ»ÐµÐºÑ‚Ñ€Ð¾Ð½Ð½Ñ‹Ð¹ ÐºÐ¾Ð¼Ð¿Ð¾Ð½ÐµÐ½Ñ‚: MH88628