CLP270M

5/24

2.3. Ringing mode

In ringing mode (Ring relay in position 2), the only protection device involved is the CLP270M.

In normal conditions, the CLP270M operates in region 1 of A1 curve, and is idle.

If an overvoltage occuring between TIP (or RING) and GND reaches the internal overvoltage reference

(+/- 270 V), the CLP270M acts and the line is short-circuited to GND. At this time the operating point

moves to region 2 for positive surges (region 3 for negative surges). Once the surge current falls below

For surges occuring between TIP and RING, the CLP270M acts in the same way. This means that the

CLP270M ensures a tripolar protection.

When used alone, the CLP270M acts at the internal overvoltage reference level (+/- 270 V). Furthermore, it

is possible to adjust this threshold level to a lower voltage by using:

Rsense

Rp

1

2

Overvoltage

reference

(+/- 270 V)

Overvoltage

detector

Overcurrent

detector

OR

TIPL

TIPS

FS

SW3 SW1

Fuse

TIP

GND

1/2 CLP270M

V

1

2

3

-270

+270

A1

Fig. 4: Switching by voltage during ringing mode.

RINGS

Rsense

Rsense

1

2

Overvoltage

reference

(+/- 270 V)

Overvoltage

detector

Overcurrent

detector

OR

Overvoltage

reference

(+/- 270 V)

Overvoltage

detector

Overcurrent

detector

OR

TIPL

TIPS

RINGL

FS

GND

SW3 SW1

SW4 SW2

1

2

Fuse

Fuse

TIP

RING

VZ1

VZ2

VZ3

VZ4

Rp

Rp

Fig. 5a: Method to adjust the reference voltage.