66 blocks are an essential component in telecommunications and network wiring, serving as a key interface for connecting various types of voice and data equipment. These punch-down blocks have been a mainstay in telephone systems since the 1960s and continue to be used in both voice and data installations today, particularly in environments where traditional telephony systems are still in place.

What is a 66 Block?

A 66 block is a type of punch-down block used to connect wiring for telephone systems and other low-voltage wiring applications. The name “66 block” comes from its Western Electric part number (type 66). It was originally designed for connecting wires in telephone systems but has since been adapted for other uses, including data networking.

Key Characteristics of 66 Blocks

• Rows and Columns: A 66 block typically features 50 rows of four IDC (Insulation Displacement Connection) terminals arranged in two sets of 25 rows. Each row consists of two sets of metal clips where wires are punched down and connected.
• Insulation Displacement: The connection is made by placing a wire in the IDC terminal and using a punch-down tool to secure it, which pushes the wire into the terminal, displacing the insulation and creating a secure electrical connection.
• Durability: 66 blocks are known for their durability and reliability, often lasting decades in a variety of conditions.

Types of 66 Blocks

There are several types of 66 blocks, each designed for specific applications. The main types include:

1. M Block

• Description: The M block is the most common type of 66 block and is typically used in telephone systems. It features four columns of pins where wires are punched down.
• Use Case: Ideal for terminating voice applications such as POTS (Plain Old Telephone Service) lines.

2. B Block

• Description: The B block is similar to the M block but includes additional bridging clips, allowing multiple connections per row.
• Use Case: Used for bridging or splitting phone lines, often seen in larger installations where more complex wiring schemes are required.

3. BR Block

• Description: The BR block is designed for data networking and is used to terminate high-speed data cabling.
• Use Case: Typically used in legacy data networks, although it has largely been replaced by modern patch panels in newer installations.

Wiring and Installation

Punching Down Wires

To install wires on a 66 block, you use a punch-down tool. The tool pushes the wire into the IDC terminal, cutting through the insulation and creating a secure connection.

Steps for Punching Down Wires:

1. Prepare the Wire: Strip about 1 inch of the outer jacket from the cable to expose the individual wires.
2. Position the Wire: Place the wire into the groove of the IDC terminal on the 66 block.
3. Punch Down: Use the punch-down tool to push the wire into the terminal. The tool will cut off any excess wire automatically.
4. Test the Connection: After all wires are punched down, use a continuity tester to ensure that the connections are secure.

Bridging Connections

66 blocks allow for easy bridging of connections, which is useful for creating splits or running multiple lines from a single source. This is typically done using bridging clips.

• Bridging Clips: Small metal clips that connect the left and right sets of pins in the same row, allowing the signal to pass through to another device or cable.
• Application: Commonly used in telephone systems to split a single phone line into multiple extensions.

Termination and Labeling

Proper termination and labeling are crucial for maintaining organized and functional wiring systems. Use a label maker or write directly on the block to identify each connection.

• Labeling: Clearly label each row or block with its corresponding line number, extension, or network device.
• Termination: Ensure that all wires are securely terminated and that there is no excess wire hanging from the block, which could cause shorts or signal degradation.

Common Applications of 66 Blocks

1. Telephony

• POTS Lines: 66 blocks are widely used for terminating traditional telephone lines in residential and commercial settings.
• PBX Systems: Often used in conjunction with Private Branch Exchange (PBX) systems to connect internal phone lines to the external phone network.

2. Networking

• Legacy Data Networks: While more common in telephony, 66 blocks have also been used to terminate data lines in older networking setups.
• Cross-Connection: Can be used in network cross-connect fields, although patch panels are more common today.

3. Alarm and Security Systems

• Alarm Wiring: Used to terminate wiring for alarm systems, sensors, and other security devices.
• Intercom Systems: Often found in older intercom systems for connecting different units within a building.

Advantages and Disadvantages of 66 Blocks

Advantages

• Durability: 66 blocks are incredibly durable and can last for decades with minimal maintenance.
• Reliability: The punch-down connections are secure and resistant to loosening over time.
• Simplicity: They are simple to install and maintain, making them a favorite for technicians familiar with traditional wiring systems.

Disadvantages

• Outdated for Data: In modern data networks, 66 blocks are largely obsolete and have been replaced by patch panels and modular jacks.
• Limited Bandwidth: Not suitable for high-speed data transmission, making them less useful in contemporary network setups.
• Space-Consuming: 66 blocks can take up a lot of physical space compared to more compact modern solutions.

Conclusion

66 blocks have been a fundamental part of telecommunications infrastructure for decades, particularly in voice applications. While they have largely been supplanted by more advanced technologies in data networking, they remain a reliable and durable solution for telephone and low-voltage wiring. Understanding the different types of 66 blocks, their installation, and their applications can help ensure that they are used effectively in both new and legacy installations. Whether you’re setting up a new telephone system or maintaining an existing one, 66 blocks offer a tried-and-true method for managing wiring connections.