Siemens 6ES5721-0CB20 Connecting Cable

The Siemens 6ES5721-0CB20 Connecting Cable links SIMATIC S5 I/O modules to termination units. This shielded cable provides reliable signal transmission for discrete and analog signals. You will find it in control cabinets across many manufacturing industries. It features a 20-pin connector on each end for secure attachment. Therefore, this cable reduces installation time and improves signal integrity.

The Siemens 6ES5721-0CB20 Connecting Cable measures 2000 mm in length and 25 mm in width. Its cable diameter reaches 8 mm for flexible routing. The unit weighs approximately 0.35 kilograms. It contains 20 individually shielded conductors for noise immunity. Two 20-pin IDC connectors terminate both ends of the cable. Additionally, you get two strain relief clamps for secure mounting.

Key Technical Specifications

Parameter	Value
Manufacturer	Siemens AG
Model	6ES5721-0CB20
Product Type	Connecting Cable
Cable Length	2000 mm (2 meters)
Number of Conductors	20
Conductor Gauge	28 AWG (7-strand)
Shielding Type	Individual foil + overall braid
Connector Type	20-pin IDC (female)
Connector Quantity	2 (both ends)
Cable Diameter	8 mm
Width	25 mm
Weight	0.35 kg
Insulation Material	PVC
Temperature Rating	-20°C to +80°C
Voltage Rating	150 V
Current Rating	1 A per conductor
Bending Radius	80 mm (minimum)

Internal Architecture and Energy Storage

The Siemens 6ES5721-0CB20 Connecting Cable stores absolutely no electrical energy internally. It contains no capacitors or active components. Twenty individually shielded twisted pairs provide excellent noise rejection. An overall copper braid surrounds all conductors for additional EMI protection. Each conductor uses 28 AWG stranded copper wire for flexibility. PVC insulation surrounds each conductor for electrical isolation. Two 20-pin IDC connectors terminate the cable at both ends. Each connector includes a polarizing key for correct orientation. The cable includes a drain wire for connecting shields to ground.

Connection Interfaces and Wiring Details

You will find a 20-pin IDC female connector at each cable end. Connect one end to the SIMATIC S5 I/O module front panel. Connect the other end to a compatible termination unit. The Siemens 6ES5721-0CB20 Connecting Cable uses color-coded conductors for easy identification. Pin 1 corresponds to the brown wire with a stripe. The cable transfers all 20 signals directly without any modification. Use the strain relief clamps to secure the connectors in high-vibration environments. The shielding works only when you properly ground the drain wire. Connect the drain wire to the ground terminal on both devices.

Installation and Routing Steps

You power off all devices before connecting this cable. First, align the connector keyway with the mating connector slot. Then, press the connector firmly until the latch engages. Tighten the strain relief screws to secure the cable. The Siemens 6ES5721-0CB20 Connecting Cable fits all S5 I/O modules with 20-pin interfaces. Route the cable away from high-voltage power cables to avoid noise. Maintain a minimum separation of 100 mm from AC power lines. Do not bend the cable beyond its minimum bending radius of 80 mm. Use cable ducts or tie wraps for organized cable management. Test both ends with a continuity checker before system startup.