Category 1 (CAT-1) is a designation for inside telephone cable primarily used for analog voice transmission. It is also referred to as Level 1 cabling.
Category 1 cabling represents the earliest level of standardized twisted pair wiring used in telecommunications. It was developed to transmit analog voice signals over telephone systems, long before the rise of Ethernet and digital networking. CAT-1 typically consists of unshielded twisted pairs (UTP) of copper conductors designed for clear voice communication rather than high-speed data. Its low bandwidth and frequency limitations make it unsuitable for modern data or broadband applications.
Although once common in residential and commercial telephone systems, CAT-1 has been replaced by higher-rated cables such as Category 3, Category 5, and Category 6, which support digital data transmission. Despite being obsolete, CAT-1 remains an important reference in the evolution of structured cabling standards, marking the foundation for modern telecommunications infrastructure.
Category 1 cabling was originally recognized under early TIA/EIA telecommunications standards and by Underwriters Laboratories (UL). Although no longer included in current TIA specifications, it contributed to the early development of cabling standardization and testing methodologies.
Introduced during the early telephone era, CAT-1 was sufficient for analog voice systems and low-speed data applications like early modems. As digital communication and Ethernet networking became standard in the late 20th century, CAT-1 was quickly phased out. Its legacy lies in its role as the first step toward structured cabling standards that now define modern communication networks.