Specification (legacy numbering)
NR/SP/TEL/30031
Signal Box Telephone Concentrator System - Design and Application Requirements (formerly RT/E/S/30031)
Issue 2, April 2006
Design rules for signal box telephone concentrators: which operator-facing features need Network Rail approval, spare capacity and expansion, spreading SPTs across line cards, designing out call blocking at peak failure traffic, and special handling of level crossing and SPT circuits.
Clause map — what each clause deals with
| 1 | Purpose | States the document sets minimum design rules for signal box concentrators and how operating rules are applied to them |
| 2 | Scope | Applies to new concentrator systems in Network Rail signal boxes and to later changes to them |
| 3 | Reference documentation | Refers to the main concentrator system specification NR/SP/TEL/30002 |
| 4 | Definitions | Defines concentrator, handset, key, lineside telephone, MMI, operator, signal box, SPT and what counts as the system |
| 5.1 | Approval of Operator's Facilities | Lists site-specific operator features Network Rail must sign off, like MMI position, key labels and colours, alerts, cord lengths and circuit reallocation |
| 6.1 | Introduction | Introduces the minimum design criteria for concentrator systems |
| 6.2 | System Expansion | Requires fitted spare line card capacity (10%) and capability to grow further (30%) without major rework |
| 6.3 | Circuit Allocation | Avoid putting two neighbouring SPTs on the same line card so one card failure does not lose both |
| 6.4 | Call Blocking Risk Reduction Requirements | System must not block calls even at worst case, every train stopped calling during degraded working; crossing calls never blocked; calculations recorded and reviewed |
| 7.1 | Introduction | Generic telephone rules sit in NR/SP/TEL/30002; this section adds extra rules for particular operational circuits |
| 7.2 | Level Crossing Telephones | Calls from AHBC/ABCL public phones get a distinctive alert that is not silenced, a differently coloured key, and a latched indication until acknowledged |
| 7.3 | Signal Post Telephones | SPT calls cannot be put on hold or into a conference |
| 7.4 | Multiple Access | A circuit may appear on more than one operator position, but SPT and level crossing circuits are not to be shared |