PCD 121 | Symmetrical Surge Coupling

PCD 121 - 6.6 kV Surge Coupling Network for Symmetrical Lines

Combination-wave surge coupling for balanced data and control lines.

The Haefely PCD 121 applies 1.2/50 us - 8/20 us combination-wave impulses up to 6.6 kV to unshielded symmetrical data and signal lines. It handles two pairs or four wires simultaneously, with manual selection of common-mode and differential-mode coupling. Decoupling is provided separately to suit the equipment under test.

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HAEFELY EMC

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TEST STANDARDS:

IEC/EN 61000-4-5 ,

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PCD 121 Datasheet V2026.06

SPECIFICATIONS

HAEFELY EMC ACCESSORIES

PCD 121 - 6.6 kV Surge Coupling Network for Symmetrical Lines

Combination-wave surge coupling for balanced data and control lines.

Overview and application

Selectable gas arrestors and ABDs keep capacitive loading low.
Pairs with DEC 5 for separate decoupling of symmetrical lines; select protection and voltage ratings for the application.
Manufacturer-listed generator equipment includes PIM 100 on the Surge Platform and PSURGE 4010. AXOS 5/8 also list PCD 121 as an accessory; choose the required generator waveform and output capability.
PCD 121 covers symmetrical combination-wave coupling. PCD 126A adds asymmetrical combination-wave and symmetrical/asymmetrical ring-wave coupling.

Technical specifications

Specification	Details
Function	Coupling network only; separate decoupling required
Line type / capacity	Unshielded symmetrical lines; up to 2 pairs / 4 wires
Impulse shape	1.2/50 us voltage - 8/20 us current; waveform defined at generator output only
Maximum impulse amplitude	6.6 kV peak
Coupling path	Manual; common mode (line-to-earth) and differential mode (line-to-line)
Series resistors	4 x 40 ohm; 4 x 80 ohm; 4 x 160 ohm
Coupling elements	90 V gas arrestors; avalanche breakdown diodes (ABDs); direct output for customer-specified elements
EUT voltage with gas arrestors	Maximum 72 V DC or 50 V AC RMS
EUT voltage with ABDs	Maximum 144 V DC or 100 V AC RMS
Signal bandwidth with gas arrestors	Greater than 10 MHz, as stated in the datasheet
Signal bandwidth with ABDs	Greater than 1 MHz, as stated in the datasheet
Connections	Safety banana sockets; supplied Fischer-Fischer HV cable
Dimensions (W x D x H)	450 x 570 x 195 mm (17.7 x 22.4 x 7.7 in)
Weight	10 kg (22 lb)

Included components

PCD 121 coupling network
1 m Fischer-Fischer HV cable
Cable set
Short-circuit bridges
User manual

Generator, EUT, auxiliary equipment and other coupling/decoupling networks are separate system equipment unless explicitly included above.

Standards and system configuration

IEC/EN 61000-4-5 Edition 2, Figure 14; Edition 3, Figure 10.

Compare data-line coupling and decoupling networks

Product	Function	Signal circuit	Test waveform	Key ratings
PCD 121	Coupling	Symmetrical; 2 pairs / 4 wires	Combination wave	6.6 kV; selectable gas arrestor / ABD coupling
PCD 126A	Coupling	4 wires; asymmetrical surge; symmetrical or asymmetrical ring wave	Combination wave; 100 kHz ring wave	6.6 kV; capacitors, ABDs, gas arrestors or direct
DEC 5	Decoupling	Symmetrical; 4 wires	Combination, telecom and ring wave	6.6 kV; 20 mH compensated; 1 A
DEC 6	Decoupling	Symmetrical; 4 wires	Combination, telecom and ring wave	6.6 kV; 200 ohm; 0.1 A
DEC 7	Decoupling	Asymmetrical; 4 wires	Combination and ring wave	6.6 kV; 20 mH uncompensated; 1.5 A
PCD-1000-4	Coupling + decoupling	Balanced Ethernet; 1 / 2 / 4 pairs; 1000Base-T	Combination wave	4 kV / 150 A surge; 65 V DC / 1 A line; IEEE 802.3af PoE

Combination wave: 1.2/50 us voltage and 8/20 us current. Telecom wave: 10/700 us voltage and 5/320 us current. Ratings depend on the selected coupling/protection elements; review each product specification before configuring the system.

PCD 121 and PCD 126A provide coupling only. DEC 5, DEC 6 and DEC 7 provide decoupling/protection only. PCD-1000-4 combines both functions for high-speed Ethernet. IP4B is an EFT/burst clamp and is intentionally excluded from this matrix.