50 Volt d.c. Fuse-Links for System X Installations to BT Specification PT1360 – Type PO

50V d.c. Fuse-Links for System X Installations to BT Specification PT1360 – Type PO Telecom Fuse | British Telecom Fuse | DC Fuse Link | BT System X Fuse

Product Introduction

The Lawson Type PO is a specialist range of Telecom Fuse links designed specifically for use in British Telecom System X installations in compliance with BT Specification PT1360. As a certified British Telecom Fuse produced to meet the exacting requirements of BT’s own procurement specification, the Type PO DC Fuse Link provides reliable, precision overcurrent protection for the sensitive 50V d.c. power distribution circuits that underpin the UK’s telephone exchange and telecommunications infrastructure.

System X was the UK’s national digital telephone switching system, developed by the UK Post Office (later British Telecom) in collaboration with GEC, Plessey, and STC, and first entering public service in 1980. System X was developed by the UK Post Office (later to become British Telecom), GEC, Plessey, and Standard Telephones and Cables (STC), with the first System X unit entering public service in September 1980 at Baynard House, London. Google Sites System X installations operate on a standard -50V d.c. power supply — the established international convention for telecommunications exchange equipment — and the Telecom Fuse links protecting these circuits must meet the specific performance, dimensional, and electrical requirements defined in BT Specification PT1360.

The Lawson Type PO British Telecom Fuse is the certified, UK-manufactured DC Fuse Link solution for System X and similar BT exchange installations, providing the precise protection characteristics required by the BT PT1360 specification to safeguard exchange power distribution equipment, line cards, switching modules, and associated telecommunications infrastructure.

Key Features

• Telecom Fuse — specialist 50V d.c. fuse-link for telecommunications exchange power distribution
• British Telecom Fuse — manufactured to BT Specification PT1360 for System X installations
• DC Fuse Link rated at 50V d.c. — suitable for the -50V d.c. power distribution standard used in UK telecommunications exchange equipment
• BT Specification PT1360 compliant — meets British Telecom’s own procurement and performance specification for System X fuse protection
• Designed for use in System X digital telephone exchange installations and similar BT telecommunications infrastructure
• Precise operating characteristics matched to the low-voltage, high-reliability requirements of telecommunications power distribution circuits
• Suitable for protecting exchange power distribution panels, line cards, switching modules, and associated telecommunications equipment
• Manufactured by Lawson Fuses under an ISO 9001 accredited quality management system — ensuring consistent, traceable production quality for critical telecommunications infrastructure

What is BT Specification PT1360?

BT Specification PT1360 is British Telecom’s own proprietary procurement specification for fuse-links used in System X digital telephone exchange installations. It defines the specific electrical performance, physical dimensions, contact configuration, operating characteristics, and test requirements that Telecom Fuse links must meet for use in BT System X power distribution equipment. The Lawson Type PO British Telecom Fuse is manufactured to comply with these requirements — providing an approved, like-for-like replacement and original equipment fuse-link solution for System X exchange maintenance, refurbishment, and ongoing operation.

What is System X?

System X is the UK’s nationally deployed digital telephone switching system, developed from the mid-1970s onwards for use across BT’s national exchange network. System X was first shown publicly in 1979 at the Telecom 79 exhibition in Geneva, Switzerland, with the first installation entering public service in September 1980. Google Sites The system operates on a -50V d.c. power supply — the standard telecommunications exchange supply voltage used internationally — distributed throughout each exchange to power switching modules, line cards, control equipment, and ancillary systems. The DC Fuse Link components protecting these power distribution circuits must meet exacting specifications to ensure exchange continuity and minimise service disruption.

Applications

The Lawson Type PO Telecom Fuse and British Telecom Fuse range is specified in:

• British Telecom System X digital telephone exchange installations — the primary application for which the Type PO is manufactured to BT Specification PT1360
• BT exchange power distribution panels — fuse protection for 50V d.c. power distribution within System X exchange equipment rooms
• Telecommunications exchange line card and module protection — individual circuit fusing within System X switching frames and equipment bays
• BT network maintenance and refurbishment — like-for-like replacement of existing PT1360 compliant DC Fuse Links in service
• Similar telecommunications infrastructure — where 50V d.c. fuse protection to comparable specifications is required in UK or international telecoms exchange environments

Why Choose Lawson Type PO British Telecom Fuse?

Telecommunications exchange equipment operates in a uniquely demanding environment — continuous 24/7 operation, zero tolerance for unplanned supply interruptions, and extremely sensitive electronic equipment that requires precisely characterised protection. A standard industrial DC Fuse Link cannot reliably provide the specific operating characteristics demanded by BT System X power distribution circuits. Only a Telecom Fuse manufactured to the exact requirements of BT Specification PT1360 can guarantee the performance consistency and reliability that exchange-critical applications require.

Lawson Fuses has been a trusted manufacturer of specialist fuse-links for telecommunications and critical infrastructure applications for decades. The Type PO British Telecom Fuse is produced under an ISO 9001 accredited quality management system with test facilities independently accredited to ISO/IEC 17025 — providing the certified, traceable performance that BT exchange maintenance teams and telecommunications infrastructure operators require when specifying replacement fuse protection for System X installations.

Q1. What is a Telecom Fuse?

A Telecom Fuse is a specialist fuse-link designed for the protection of telecommunications power distribution circuits — particularly the low-voltage d.c. power supplies used in telephone exchange, data centre, and telecoms network infrastructure. Unlike standard industrial or household fuses, a Telecom Fuse is engineered to meet the specific operating characteristics, voltage ratings, and performance requirements of telecommunications power systems — including precise current ratings, low voltage d.c. capability, and high reliability for continuous 24/7 operation. The Lawson Type PO is a Telecom Fuse manufactured to BT Specification PT1360 for use in System X telephone exchange installations at 50V d.c.

Q2. What is a British Telecom Fuse?

A British Telecom Fuse is a fuse-link manufactured to comply with British Telecom’s own proprietary specifications for use in BT exchange and network equipment. BT developed its own fuse specifications — including PT1360 for System X installations — to ensure that fuse-links used in its critical exchange infrastructure meet precisely defined performance, dimensional, and reliability requirements. The Lawson Type PO British Telecom Fuse is produced to BT Specification PT1360, making it the correct approved DC Fuse Link for System X exchange maintenance and operation.

Q3. What is BT Specification PT1360?

BT Specification PT1360 is British Telecom’s proprietary procurement and performance specification for fuse-links used in System X digital telephone exchange power distribution. It defines the electrical operating characteristics, physical dimensions, rated voltage (50V d.c.), contact configuration, and test requirements that a Telecom Fuse must satisfy for use in BT System X equipment. The Lawson Type PO is manufactured specifically to comply with PT1360 — providing a certified, like-for-like British Telecom Fuse for System X installation and maintenance.

Q4. What is a DC Fuse Link and why is it different from an AC fuse?

A DC Fuse Link is a fuse-link specifically rated and designed for direct current (d.c.) circuit protection. DC fuse links differ from AC fuses in several important ways: DC circuits do not have a natural current zero-crossing (as AC circuits do every half-cycle), meaning that arc extinction after fuse operation is significantly more demanding in DC applications. A DC Fuse Link must therefore be specifically engineered to interrupt and extinguish a DC arc reliably and safely. The Lawson Type PO is a 50V d.c. Telecom Fuse rated specifically for the d.c. power distribution circuits used in BT System X exchange equipment.

Q5. What is System X and why does it require a specialist Telecom Fuse?

System X is the UK’s national digital telephone switching system, deployed by British Telecom across its exchange network from the early 1980s onwards. It operates on a standard -50V d.c. power supply — the international convention for telecommunications exchange equipment — distributed throughout each exchange building to power switching modules, line cards, and control equipment. The power distribution circuits within System X exchanges require Telecom Fuse links that meet BT’s specific PT1360 performance specification, as standard industrial or domestic fuses are not designed or tested for the precise operating characteristics demanded by telecommunications exchange power distribution systems.

Q6. What voltage is the Lawson Type PO Telecom Fuse rated for?

The Lawson Type PO British Telecom Fuse is rated at 50V d.c. — matching the standard -50V d.c. power supply voltage used in BT System X telephone exchange installations and similar telecommunications exchange infrastructure throughout the UK.

Q7. Can the Type PO Telecom Fuse be used as a direct replacement in existing System X installations?

Yes. The Lawson Type PO DC Fuse Link is manufactured to comply with BT Specification PT1360 — the same specification to which original equipment fuse-links in System X installations are made. This makes the Type PO a certified like-for-like replacement for existing British Telecom Fuse links in System X exchange power distribution panels and equipment bays. Always confirm the current rating and PT1360 compliance before installing any replacement fuse in BT exchange equipment.

Q8. Is the Lawson Type PO available to BT approved contractors and telecoms maintenance engineers?

Yes. The Lawson Type PO Telecom Fuse range is available through the Lawson Fuses sales team and their authorised sales partners and electrical wholesalers across the UK. It is suitable for supply to BT approved contractors, telecommunications infrastructure maintenance companies, and independent telecoms engineers carrying out authorised work on System X exchange equipment. Contact Lawson Fuses directly for trade pricing, availability, and technical support.

Q9. Are other telecom and DC fuse variants available from Lawson?

Yes. Lawson Fuses manufactures a broad range of specialist and standard fuse-links for telecommunications, data centre, power conversion, and DC application requirements beyond the Type PO BT PT1360 range. The Type MIN Miniature Fuse range covers low-current electronics and telecom circuit protection, and the Type LSC Semiconductor Fuse range covers power conversion rectifier and inverter protection. Contact the Lawson Fuses sales team or download the Short Form Catalogue for full details of available products for telecommunications and DC applications.

Q10. How do I order the Lawson Type PO British Telecom Fuse?

The Lawson Type PO Telecom Fuse range — manufactured to BT Specification PT1360 for System X DC installations — is available through the Lawson Fuses sales team and their network of authorised sales partners and electrical wholesalers across the UK. Contact Lawson Fuses directly for trade pricing, availability by current rating, and technical support for your System X exchange maintenance or BT infrastructure project.