The Current Situation of Large-diameter Coaxial Cables in Network Cabling

The large-diameter cable (also known as large-diameter wire cable or multi-pair cable) plays a primary role in network cabling (especially in the integrated cabling system) as the main transmission medium for voice. It is used to efficiently and with high capacity carry telephone voice signals, some low-speed data, or traditional communication services. It is not the mainstream data network backbone (nowadays, the data backbone is mostly made of optical fibers or 6-category/ultra-6-category 4-pair twisted wires), but it still holds an important position in many practical projects, especially in hybrid weak current systems.

Main Functions and Application Scenarios

1. Voice Backbone (The Most Core and Common Function)

- In the building's comprehensive wiring system, it is used for the vertical backbone subsystem (from the main equipment room/telecommunication room to each floor distribution room) or the horizontal subsystem for large-capacity voice convergence.

- One 25-pair large-diameter cable can simultaneously support 25 analog telephones (or some digital telephones/PBX extensions), 50 pairs support 50, 100 pairs support 100... significantly reducing the number of wiring and the occupation of conduits.

- Typical scenarios: Telephone main control rooms in office buildings, hotels, hospitals, schools, community properties, industrial parks, etc. → Backbone connections from the main control room to the distribution boxes on each floor/area.

2. Traditional Telephone Access and Convergence

- When telecom operators introduce telephone trunk lines into buildings, they often use large-diameter cables (hundreds or even thousands of pairs).

- Property/weak current shafts → Each unit/floor → Office/room distribution, often using 50-pair or 100-pair large-diameter cables for intermediate convergence.

3. Some data/broadband early applications (gradually decreasing)

- 3-category thick twisted pair: Mainly for voice, with very low bandwidth (≤ 16 MHz).

- 5-category/ultra-5-category thick twisted pair (less common): Capable of supporting 100 Mbps or even gigabit Ethernet (1000BASE-T), used for early broadband user access, VDSL convergence, or certain low-cost data trunk lines. However, it has now largely been replaced by fiber optic or multiple Cat6A cables.

4. Other Special Applications

- Radio paging systems, multi-channel audio transmission.

- Some low-speed multi-channel multiplexing of video surveillance or control signals (rare cases).

- During the renovation of old buildings, the existing large-diameter ducts are utilized to continue carrying voice signals.

Summary: In modern network cabling, the main function of large gauge cables is to "efficiently and cost-effectively solve the vertical/master trunk convergence of a large number of telephone lines", serving as the backbone of the voice component in the integrated cabling system, rather than being the core transmission medium of the data network.

Large-diameter coaxial cables have not been completely phased out in network cabling, but they have indeed been significantly marginalized and are currently in a "predominantly existing, with very few new installations" stage. By 2026, they have largely ceased to be the mainstream choice in most newly built or upgraded modern integrated cabling systems, but they still exist in large quantities and continue to be used in many practical scenarios.

Current (2026) real situation summary

- New projects (especially data centers, intelligent buildings, high-end office buildings):

Almost 100% elimination of large gauge cables.

- Voice traffic is all carried via VoIP/IP phones → using ordinary Cat6/Cat6A network cables (even fiber to the desk) is sufficient.

- Data backbone/vertical trunk lines → optical fiber (OM5 multimode or single-mode) + short-distance copper cables (Cat8, etc.).

- The standards for comprehensive wiring (such as TIA-568, GB 50311) have not recommended large gauge cables as voice trunk lines for many years; new regulations directly lead to full IPization.

- Existing buildings/old systems (still accounting for a large proportion):

Large-diameter cables have not been phased out and are still widely in use:

- Traditional hotels (PBX systems), hospitals, schools, old office buildings, government agencies, industrial parks.

- Property/telecommunication trunk lines or floor convergence still use 50-pair, 100-pair, 200-pair large-diameter cables.

- Many buildings installed their cables between 2000 and 2015 and are now reaching the mid-life stage (copper cores are durable and have low attenuation), so they can continue to be used for another 5-15 years without replacement.

- During renovations, "use what works" is often adopted, unless the entire floor is re-laid, in which case they will not be replaced.

- Some transitional/hybrid scenarios are still in use:

- Some small and medium-sized enterprises/parks are still building or expanding traditional analog/digital telephone systems (low cost, compatible with old equipment).

- Certain special places (such as old elevator intercoms, fire alarm phones, and broadcasting systems) still rely on large gauge cables.

- The last segment of "copper cable access" from telecom operators still has a stock in remote or old residential areas.

Why hasn't it been completely phased out?

- Economic aspect: Replacing the entire building's large-diameter trunk lines is costly (including conduit installation, hole drilling, and work stoppage), while a VoIP converter/gateway can convert the existing large-diameter lines to IP phones for just a few hundred yuan.

- Compatibility: A large number of old-fashioned telephones, attendance machines, access control systems, and alarm hosts still only support traditional lines.

- Reliability: Pure copper large-diameter lines have lower attenuation and are more stable in long-distance and low-speed voice scenarios, and they can still make calls even in the event of power failure (VoIP relies on the network and power supply).

Future Trends (2026–2030)

- Accelerated Elimination: As operators completely shut down PSTN (in some parts of China, the "fixed-line IPization" or "copper withdrawal and optical insertion" process has been initiated), and VoIP/Cloud PBX becomes widespread, the demand for large-diameter cables will further decline.

- Complete Exit from Mainstream: It is expected that by around 2030, the proportion of large-diameter cables in new projects will be close to 0%, but the existing cables will still be in service for a long time (similar to the use of Category 5 cables in many places).

- Alternative Solutions: Use network cables + PoE for telephone equipment, or directly fiber to floors or desks.