Substitution Electrical Systems
Replacement of electronic systems or devices
Substitution, derived from the Latin word *substitutio* (replacement), describes, in the field of electronic devices, the process of replacing a part, a component or an entire device with a functionally equivalent or even improved element. This process is necessary or beneficial in many situations and may be carried out for various reasons.
A common reason for substitution is availability. If a component is no longer available, for example due to the end of production or supply bottlenecks, a replacement must be found. A classic example of this is the replacement of a microchip that is no longer manufactured with a compatible model.
Another important aspect is cost optimisation. Here, expensive components are replaced by cheaper alternatives that nevertheless offer the same or even better performance. For example, an expensive capacitor could be replaced by a cheaper but more powerful model.
Technological advancement also plays a central role. Obsolete components are replaced by modern, more efficient or more powerful parts. A typical example is the replacement of a conventional hard disk drive (HDD) with a solid-state drive (SSD), which enables faster data processing.
Substitution is also indispensable in the context of repair and maintenance. Faulty components are replaced with functioning ones to restore the device’s functionality. A common example is the replacement of a faulty power supply unit in a computer.
Last but not least, environmental or safety requirements may necessitate substitution. Harmful or non-compliant materials, such as lead in solder, are replaced with more environmentally friendly or safer alternatives. An example of this is the replacement of components that do not comply with the RoHS (Restriction of Hazardous Substances) directives.
However, there are also challenges to consider when it comes to substitution. The compatibility of the replacement component must be ensured – electrically, mechanically and functionally. Furthermore, performance adjustments must be made, as specifications such as voltage, current or dimensions may differ. In certain sectors, such as medical or aerospace engineering, replacement parts must also have specific certifications.
There are many practical examples of substitution: replacing a 100-ohm resistor with one having the same resistance value but a higher current-carrying capacity; swapping a transistor for a model with greater efficiency; or replacing an entire display in a smartphone with a compatible model from another manufacturer.
Traction power supply systems · Critical infrastructure
the function does.
We replace discontinued components in railway power supply systems with functionally equivalent successor solutions. We do so using a systematic approach, in compliance with standards, and with comprehensive documentation to support ongoing operations.
Obsolescence
Manufacturers are ceasing production. Stock levels have been depleted. The plant is still running — but there are no spare parts.
Risk of downtime
Any component that cannot be sourced constitutes an unplanned outage on hold. This is not an acceptable option in the railway supply chain.
Approval pressure
Outdated components no longer comply with standards. Continuing to use them without up-to-date certification poses legal and safety risks.
Our service –
Methodical substitution
We analyse what the component needs to do — not what it looks like. The result: a replacement component with the same functionality that meets all regulatory and operational requirements.
Review of the current situation
We review all available documentation: data sheets, circuit diagrams, test reports and approvals. Feedback from the field and failure history are taken into account, as is the operator’s remaining stock.
Data sheet
Circuit diagram
Field data
Stock levels
Functional Specification
We draw up a manufacturer-neutral specification of requirements — electrical, mechanical, thermal and safety-related. Fail-safe behaviour and SIL requirements are explicitly defined and documented.
Standards
Safety (SIL)
Interfaces
Operation
Testing and Acceptance
Component selection
Market research based on the specification, technical comparison and evaluation matrix. Only candidates with a documented lifecycle commitment of at least 10–15 years will be shortlisted.
Market research
Lifecycle
Assessment matrix
Engineering
With our WITT-Bridge modular system, which has been specially developed to meet the requirements of railway power supply systems, we are replacing the functionality of older measurement, control and regulation systems with modern, versatile modules.
Compatibility
Retrofit capability
Cost savings
Qualification test
Tests under real-world railway conditions: shock, vibration, thermal cycling, EMC, voltage dips, long-term testing. Acceptance by an accredited testing body; the results form part of the approval dossier.
EN 61373
EN 50121
EN 60068
Testing centre
Documentation & Approval
Mapping documentation, test reports, change history in accordance with CSM-RA, and updates to the safety case. All archived in an audit-proof manner for the entire service life of the plant plus 10 years.
CSM-RA
Safety certificate
EBA
Long-term archive
Old component
Discontinued — no longer available
- Same interfaces
- Same face values
- Same protection class
- Identical safety requirements
=
IDENTICAL FUNCTION
New component
Modern — available in the long term
- Modern technology platform
- Advanced diagnostics
- Lifecycle-Commitment: 10–15 years
- Full compliance with standards
What you can win
System availability ensured
No unplanned downtime due to a lack of spare parts. The traction power supply remains operational without interruption.
Documentation in accordance with standards
Support special exhibitons.
All documentation relating to operational authorisation, EBA requirements and audits — complete, audit-proof and immediately accessible.
Planning certainty
Successor components with a documented lifecycle commitment. No risk of obsolescence in the foreseeable future.
Investment protection
Existing infrastructure and installations remain fully operational. No refurbishment, no starting from scratch.
Advanced diagnostics
New technology often provides status updates and diagnostic data that actively support maintenance — added value without any extra effort.
A point of contact
Analysis, procurement, testing and documentation, all from a single source. No need to coordinate between different service providers.
