# EM84

> Main use as tuning indicator in radios

**Wikidata**: [Q1275149](https://www.wikidata.org/wiki/Q1275149)  
**Source**: https://4ort.xyz/entity/em84

## Summary
The EM84 is a vacuum tube model introduced in 1957, primarily used as a tuning indicator in radios to visually display signal strength through its characteristic glowing response. It belongs to the magic eye tube class, which provides a visual representation of electronic signal amplitude.

## Key Facts
- Introduced in 1957 as a vacuum tube model for radio tuning indicators
- Manufactured by Koninklijke Philips NV
- Classified as a magic eye tube subclass for visual signal amplitude indication
- Complies with Mullard–Philips tube designations standard
- Documented in Philips datasheet (retrieved September 3, 2016)
- Has 3 Wikipedia sitelinks (Commons, German, Polish editions)
- Registered in Google Knowledge Graph under ID /g/121bd37g
- Identified in Radio Museum database as vacuum tube ID "em84"

## FAQs
### Q: What is the primary function of the EM84?  
A: The EM84 serves as a tuning indicator in radios, visually displaying signal strength through its glowing response to guide users when aligning radio stations.

### Q: When was the EM84 manufactured?  
A: It was introduced in 1957 by Koninklijke Philips NV as part of their vacuum tube lineup.

### Q: What category does EM84 belong to?  
A: It is classified as a magic eye tube, a specialized vacuum tube type designed to visually indicate electronic signal amplitude.

### Q: Is the EM84 still in production?  
A: Production details are not provided in the source material, but its introduction in 1957 suggests it is a historical model.

## Why It Matters
The EM84 played a crucial role in enhancing user experience for mid-20th century radio receivers. As a tuning indicator, it transformed the abstract process of aligning radio frequencies into an intuitive visual signal, allowing users to precisely tune stations with minimal technical knowledge. This innovation represented a significant advancement in human-computer interaction for consumer electronics, bridging the gap between analog electronic signals and human perception. Though largely replaced by modern digital displays, the EM84 remains a landmark example of how visual feedback simplified complex electronic operations, influencing later interface design principles in consumer audio equipment.

## Notable For
- Being a landmark example of magic eye tube technology for consumer radio tuning
- Its 1957 introduction by Koninklijke Philips NV as a standardized vacuum tube model
- Compliance with Mullard–Philips designations, facilitating industry-wide compatibility
- Visual signal indication that made radio tuning more accessible to non-technical users
- Documentation in Philips technical datasheets, preserving its engineering specifications

## Body
### Overview
The EM84 is a vacuum tube model introduced in 1957, primarily deployed as a tuning indicator in radios. It functions by providing a visual representation of signal strength, enabling users to optimize radio reception through its distinctive glowing response.

### Technical Classification
- **Instance**: Vacuum tube model
- **Subclass**: Magic eye tube
- **Designation Compliance**: Mullard–Philips tube designations
- **Core Function**: Visual indication of electronic signal amplitude

### Documentation
- **Datasheet**: Available at http://frank.pocnet.net/sheets/010/e/EM84.pdf (English language, PDF format, accessed 2016-09-03)
- **Museum ID**: em84 (Radio Museum database)
- **Google Knowledge Graph ID**: /g/121bd37g
- **Wikipedia Presence**: Sitelinks in 3 languages (Commons, German, Polish)

### Historical Context
- **Manufacturer**: Koninklijke Philips NV
- **Introduction Year**: 1957
- **Primary Application**: Radio tuning indicators
- **Legacy**: Preserved as a technical reference in vacuum tube engineering documentation

## References

1. [Source](http://frank.pocnet.net/sheets/010/e/EM84.pdf)