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AN34

Secondary Line Protection for T1 and E1 Line Cards

Cirrus Logic 

T1/E1 Line Protection

Equipment designed to connect to outside lines

is subject to the first level longitudinal and me-

tallic surge tests summarized in Table 2. After

these tests the equipment must function cor-

rectly.

Surge

Min.

Voltage3

[Vpk]

Rise/

Decay

Time [µs]

Min.

Current

[A]

Repetitions

Each

Polarity

1. L,M

±600

10/1000

100

25

2. L,M

±1000

10/360

100

25

3. L,M

±1000

10/1000

100

25

4. L

±2500

2/10

500

10

5. L

±1000

10/360

25

5

Notes:

1. L = Longitudinal Mode, M = Metallic Mode

2. Surge 3 is optional in place of Surges 1 and 2.

3. These tests are repeated at a voltage just below the

operating threshold of any secondary protectors.

4. Primary protectors removed.

Table 2. TR-NWT-001089 First Level Lightning Surges

Upon completion of the first level test, the sec-

ond level longitudinal surge test in Table 3 is

conducted. After this test, the equipment may be

damaged but must not pose a fire, fragmentation

or electrical safety hazard.

Surge

Min.

Voltage3

[Vpk]

Rise/

Decay

Time [µs]

Min.

Current

[A]

Repetitions

Each

Polarity

1. L

±5000

2/10

500

1

Notes:

1. L = Longitudinal Mode

2. Primary protectors removed.

3. Repeated at a voltage just below the operating threshold

of any secondary voltage limiting device.

Table 3. TR-NWT-001089 Second Level Lightning

Surges

Customer Premises Equipment (CPE) designed

for use only on inside lines (i.e., type 4 equip-

ment) is tested to the intra-building lightning

immunity requirements in Table 4. To pass the

intra-building lightning surge testing, the equip-

ment must not be damaged. This test consists of

a TIP/RING metallic surge of each polarity and

a longitudinal surge of each polarity from TIP

and RING to chassis ground.

AN34REV1

Surge

Min.

Voltage3

[Vpk]

Rise/

Decay

Time [µs]

Min.

Current

[A]

Repetitions

Each

Polarity

1. L,M

±800

2/10

100

1

2. L

±1500

2/10

100

1

Notes:

1. L = Longitudinal Mode, M = Metallic Mode

2. Primary protectors removed.

3. Repeated at a voltage just below the operating threshold

of any secondary voltage limiting device.

Table 4. TR-NWT-001089 Intra-Building Lightning

Surges

Current Limiting Protector Test

The current limiting protector test applies to

equipment connected to outside lines (type 1 and

3 systems), and it is designed to verify that the

equipment has a time vs. current fusing charac-

teristic which will limit fault current enough to

prevent it from becoming a fire hazard or ignit-

ing the building wiring. Fuse links are provided

on outside lines which might come in contact

with AC power lines, but these links are only

designed to meet the current handling limitation

of the carbon block primary protectors and not

those of downstream network equipment and

wiring.

A Bussman MDQ 1.6 Ampere fuse is used in the

test to simulate the fusing characteristics of

premises wiring. During the test a 60 Hz, 600

VAC source is applied differentially to the tele-

communication ports for 15 minutes. If the 1.6 A

fuse breaks or the equipment under test becomes

a fire hazard, then it must be specified for use

only with external current-limiting protectors.

This protection is typically provided by a 350

mA heating coil installed between the equipment

and the primary voltage-limiting protector.

Short Circuit Immunity

The equipment under test must not be damaged

or require any manual intervention after 30 min-

utes of operation with: 1) TIP shorted to RING,

2) TIP shorted to ground with RING floating, 3)

RING shorted to ground with TIP floating, or 4)

TIP and RING both grounded. Also, the equip-

5

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