Reference & Cheatsheet

Fifteen volumes back, this series opened with a spinning disc of darning needles and bicycle-lamp lenses in a rented Hastings room, and it has since carried that one idea — decompose a picture into a stream of light, transmit the stream, reconstruct the picture — through a century of names, numbers, dates, and technical terms: Nipkow, Baird, Jenkins, Mihály, Rosing, Takayanagi, Phonovision, Emitron, Telechrome, the NBTVA. No reader is expected to have memorised all of it, and no reader should have to page back through fourteen volumes to check whether the Baird standard ran at 12.5 or 7.5 frames per second, or whether a genuine Nipkow disc’s holes were round or square. This volume exists to answer exactly those questions in one place: a standards table with the numbers that matter, a glossary of every recurring term, a timeline of the whole story end to end, a roster of the people who built it, a list of where the real hardware lives today, a short shelf of further reading, and an index back into every volume above. Read it start to finish if you like, but it is built to be opened at a single page and closed again — the volume to bookmark, not to read once and shelve.

16.1 Standards Table: Baird 30-Line vs. NBTV 32-Line

The single most-referenced table in this series. Every number below is checked against the verified-facts research record (§4 for the Baird standard, §8b/§8d for the modern NBTVA standard) and is not restated differently anywhere else in this series.

Table 1 — Standards Table: Baird 30-Line vs. NBTV 32-Line

Parameter	Baird 30-line (BBC broadcast standard, 1929–35)	NBTV 32-line (modern NBTVA club standard)
Lines per frame	30	32
Frame rate	12.5 fps	12.5 fps
Lines per second	375 (30 × 12.5)	400 (32 × 12.5)
Line scan	Vertical, bottom to top	Vertical, bottom to top
Frame scan	Horizontal, right to left	Horizontal, right to left
Aspect ratio (height:width)	7:3, portrait	3:2, portrait
Video bandwidth	~10 kHz in practice (~13 kHz theoretical)	2 Hz–10 kHz at −3 dB
Scanning method	Progressive (no interlace)	Progressive (no interlace)
Signal amplitude	Not standardised to a specific voltage in surviving records	1 volt peak-to-peak
Video polarity	Not standardised in surviving records	White most positive, black most negative
Sync pulses	An ordinary black bar between lines — no “blacker-than-black” scheme; consequently, an all-black picture could not be transmitted without losing sync, so black pictures were never permitted on the BBC service	”Blacker than black” — 33%–50% more negative than black level, AC-coupled
Frame sync	Achieved by disc geometry and motor synchronisation (no missing-pulse convention documented)	The line-sync pulse is deliberately omitted between line 32 and line 1; video is held black during the gap
Disc rotation (typical club practice)	Not separately standardised in surviving records	Anti-clockwise; viewing position on the disc: right

A footnote worth reading before quoting the 7:3 figure elsewhere: the NBTVA’s own standards.htm notes that on the actual Baird Televisor, “the first three and last three lines were made wider and spaced further apart” than the rest, which altered the effective aspect ratio of the viewed picture to something closer to 2:1 — so 7:3 is the nominal scanning-geometry ratio, not necessarily the exact shape of the picture a Televisor owner actually saw. Both figures are correct; they answer slightly different questions, and this volume keeps them straight rather than picking one.

A third historical variant is worth a single mention for context, without complicating the table above: a German standard used by the TeKaDe receiver ran 30 lines at 375 lines/sec like Baird’s, but scanned horizontally left-to-right for the line and vertically top-to-bottom for the frame — a landscape orientation, aspect ratio 3:4 — proof that the vertical-line/horizontal-frame/portrait choice common to both standards in the main table was a design decision, not a physical necessity of the scanning-disc principle itself.

Glossary

Alphabetical. Each entry is one to two sentences; volume numbers point to where a fuller treatment lives.

Aperture (scanning hole). One of the perforations in a Nipkow disc’s spiral, through which light passes to (or from) the photocell or lamp behind it. Genuine production Baird Televisor discs are documented with square-section apertures, not round ones — do not describe Baird holes as circular (Vol 6, Vol 13, Vol 14).
Aspect ratio (portrait). The height-to-width proportion of the scanned image; both the Baird (7:3) and NBTV (3:2) standards scan a picture taller than it is wide, suited to a single head-and-shoulders subject (Vol 4, Vol 16).
Bandwidth (video). The range of frequencies a video signal occupies; both mechanical standards keep their bandwidth low enough to fit within an ordinary audio channel — around 10 kHz for Baird, 2 Hz–10 kHz for NBTV (Vol 4, Vol 12).
Blacker-than-black sync. The modern NBTV convention of driving the sync pulse 33%–50% more negative than the video’s own black level, so a receiver can distinguish “sync” from “genuinely black picture content” even during an all-black scene — something the historical Baird signal could not do (Vol 12).
Club Sales. The NBTVA’s members-only parts shop — pre-drilled discs, motors, driver boards, and free CAD files — the practical, low-cost route into building a working modern receiver (Vol 11, Vol 14).
Condenser lens. A lens (often salvaged from a slide projector) placed behind a Nipkow disc to concentrate the light diverging from a single scanning aperture onto the photocell (Vol 13).
Emitron. The camera tube developed by EMI for the Marconi-EMI 405-line system; the electronic camera that beat Baird’s mechanical/intermediate-film system at Alexandra Palace (Vol 10).
Flying-aperture (receiver). A receiving Nipkow disc’s aperture, sweeping past a fixed lamp, reconstructing the image line by line — the mirror image, at the display end, of the flying-spot scan at the camera end (Vol 4).
Flying-spot (scanner). A scanning method in which a moving spot of light is projected onto the scene or onto film, with a fixed photocell reading the reflected or transmitted brightness; used in Baird’s later studio cameras and intermediate-film scanners (Vol 4, Vol 9).
Framing / phasing. The manual controls on a Televisor (or a modern disc receiver) that adjust the disc’s rotational position relative to the incoming signal so the picture sits square in the viewing window rather than sliding sideways or wrapping around (keystoned or torn) (Vol 6, Vol 13).
Gamma. The non-linear relationship between a display’s input signal and its output brightness; a plain neon-lamp or LED disc televisor is close to gamma = 1 (linear), unlike a CRT (gamma ≈ 2), which is why unmodified broadcast-style video can look “bleached out” on a linear disc set (Vol 13).
Iconoscope. Vladimir Zworykin’s camera tube design for RCA, patented (in application) 1923 but not working until 1933; the American electronic counterpart to EMI’s Emitron (Vol 10).
Intermediate film (system). A television method in which a scene is filmed on ordinary movie film, rapidly developed (in roughly 45 seconds), and then scanned by a flying-spot scanner — a workaround for early electronic cameras’ insufficient light sensitivity, used by both Fernseh AG and Baird (Vol 9).
Keystone distortion. A trapezoidal warping of the scanned picture caused by imperfect disc-to-lamp or disc-to-lens geometry; one of the practical faults a framing/phasing adjustment is meant to correct (Vol 6, Vol 13).
Line scan. The direction in which a single scanning line is traced; both the Baird and NBTV standards trace each line vertically, bottom to top (Vol 4, Vol 16).
Lines per frame. The number of scan lines that make up one complete picture; 30 for the Baird standard, 32 for modern NBTV (Vol 4, Vol 16).
Low Definition Television Association (LDTVA). The original 1975 name of the club later renamed, in 1978, the Narrow-Bandwidth Television Association (Vol 11).
Mirror drum. A scanning device using angled mirror facets around the circumference of a spinning drum, each facet sweeping the light beam across one scan line; the technique the BBC itself favoured in its studio cameras from 1932 (Vol 9, Vol 11).
Mirror screw. A helical, “spiral staircase” arrangement of mirror facets on a rotating shaft, one facet per line; capable of larger, brighter images than a disc scanner but demanding critical alignment and polish tolerances (Vol 9, Vol 11).
Missing-pulse frame sync. The modern NBTV convention that marks the start of a new frame not by adding a special pulse but by deliberately omitting the ordinary line-sync pulse that would otherwise fall between line 32 and line 1 (Vol 12, Vol 13).
Narrow-Bandwidth Television (NBTV). The modern hobbyist standard and signal convention — 32 lines, 12.5 fps, audio-bandwidth video — that keeps the scanning-disc tradition alive today (Vol 11, Vol 12).
Narrow-Bandwidth Television Association (NBTVA). The international hobbyist club, founded 1975 (as the LDTVA), that defines and maintains the modern 32-line standard, sells parts, and holds an annual Convention (Vol 11).
Neon lamp (flat-plate). The glow-discharge lamp used as the display element in a Baird Televisor and in some modern club builds; neon’s emission spectrum is essentially monochrome orange, which is why every historical mechanical television picture was rendered in shades of orange rather than grey (Vol 4, Vol 6).
Nipkow disc. A flat disc pierced near its edge with a single-turn spiral of apertures; rotating it in front of a scene (or a lamp) decomposes (or reconstructs) an image line by line. Conceived by Paul Nipkow in 1884 and never built by Nipkow himself (Vol 3).
Persistence of vision. The perceptual effect by which the eye fuses a rapid enough sequence of still images into the impression of continuous motion; the practical threshold used throughout this series is roughly 10–16 complete frames per second (Vol 2).
Phonovision. John Logie Baird’s experimental method (1927–28) of recording a 30-line television signal directly onto a wax gramophone disc, because the signal’s audio-range bandwidth allowed it to be cut like ordinary sound; the world’s first television recordings, forensically recovered decades later by Donald McLean (Vol 8).
Progressive scanning. Scanning every line of a frame in a single, uninterrupted pass, without interlacing separate half-frames — the method used by both the Baird and NBTV standards (Vol 4).
Radiovisor / Radiovision. Charles Francis Jenkins’s American mechanical-television receiver and transmission method, using a lensed scanning disc; demonstrated silhouette (not tonal) images from June 1925 (Vol 7).
Scan converter. A modern electronic device that translates an NBTV signal to and from ordinary broadcast-style (CCIR) video, letting an unmodified camcorder or television act as an NBTV source or display (Vol 11, Vol 12).
Scophony (system) / Jeffree cell. A 1930s large-screen mechanical television system using rotating mirror drums and an acousto-optic light modulator (the Jeffree cell, 1934) to project images many feet across; demonstrated at Radiolympia 1938 on the 405-line BBC signal, not the 30-line standard (Vol 9).
Selenium cell. A photoconductive element — its electrical resistance falls as light falling on it increases — first characterised by Willoughby Smith in 1873; the basic light-sensing component behind every 19th- and early 20th-century image-transmission proposal, including the Nipkow disc’s transmitter side (Vol 2, Vol 3).
Telechrome. Baird’s fully electronic, cathode-ray-tube colour television system, first shown in 1944; not a mechanical system, and the technological endpoint of Baird’s own colour-television work (Vol 9).
Telehor. Dénes von Mihály’s mechanical television system and company name (Hungary/Germany); publicly demonstrated 1928 and 1931 (Vol 7).
Televisor. John Logie Baird’s trademarked brand name for his mechanical television receiver, sold commercially in Britain from 1930 (Vol 3, Vol 5, Vol 6).

16.2 Timeline: 1873 to Today

Figure 1 — A full reference timeline of mechanical television, from Willoughby Smith's 1873 discovery of selenium's light-sensitivity through Paul Nipkow's unbuilt 1884 patent, Baird's first television image … — Figure 1 — A full reference timeline of mechanical television, from Willoughby Smith's 1873 discovery of selenium's light-sensitivity through Paul Nipkow's unbuilt 1884 patent, Baird's first television image and the BBC 30-line broadcast era, the 1936–37 Alexandra Palace trial that handed victory to electronic television, the 1975 founding of the NBTVA, and the modern 32-line hobby still active today. Each marker is labelled with the volume(s) that cover it in depth. Original diagram for this series, drawn from the dates verified throughout Vol 2–15 and the verified-facts research record. — original diagram, this series

Table 2 — Timeline: 1873 to Today

Year	Event	Volume
1873	Willoughby Smith discovers selenium’s light-sensitivity	Vol 2
1884	Paul Nipkow patents the scanning disc (never built)	Vol 3
1911	Boris Rosing demonstrates mirror-drum transmission to a CRT receiver	Vol 7
13 Jun 1925	Jenkins transmits a silhouette image (Radiovision, US)	Vol 7
2 Oct 1925	Baird transmits the first tonal (grey-scale) television image	Vol 5
26 Jan 1926	Royal Institution demonstration — first public/press demo of true television	Vol 5
25 Dec 1926	Takayanagi demonstrates a Nipkow-disc-to-CRT hybrid system (Japan)	Vol 7
Sep 1927	Farnsworth transmits the first fully electronic image	Vol 10
Feb 1928	First transatlantic television transmission	Vol 5
Jul 1928	Baird’s first colour television demonstration	Vol 9
Aug 1928	Baird’s stereoscopic television demonstration; Berlin Funkausstellung publicly credits Nipkow	Vol 3, Vol 9
1929	BBC 30-line broadcast service begins; Fernseh AG formed (Germany)	Vol 7, Vol 8
1930	The Televisor goes on public sale	Vol 6
1931	Soviet 30-line broadcasts begin; Mihály demonstrates in Berlin	Vol 7
1932	Intermediate-film television demonstrated (Fernseh AG, then Baird)	Vol 9
Mar 1935	Fernsehsender “Paul Nipkow” opens in Berlin — world’s first regular public TV station	Vol 3
Sep 1935	BBC 30-line service ends (11 September)	Vol 8
Nov 1936	Alexandra Palace service opens, alternating Baird and Marconi-EMI systems	Vol 10
Feb 1937	The Baird system is dropped; 405-line electronic television wins	Vol 10
1938	Soviet television transitions to electronic standards	Vol 7
Aug 1940	Paul Nipkow dies; given a state funeral broadcast live on television	Vol 3
Aug 1944	Telechrome, Baird’s electronic colour CRT system, demonstrated	Vol 9
1948	Scophony merges with John Logie Baird Ltd	Vol 9
1975	The Narrow-Bandwidth Television Association founded (as the LDTVA)	Vol 11
1978	Renamed the Narrow-Bandwidth Television Association (NBTVA)	Vol 11
1982–2000	Donald McLean recovers the Phonovision discs; publishes Restoring Baird’s Image	Vol 8, Vol 11
Today	The NBTVA remains active: quarterly Newsletter, annual Convention, live forum, Club Sales	Vol 11–15

16.3 Key Figures

Table 3 — Key Figures

Figure	Role	Volume
Willoughby Smith	Discovered selenium’s light-sensitivity (1873), the basic sensing effect behind every early image-transmission scheme	Vol 2
Paul Nipkow	Patented the scanning-disc principle (1884); never built a working set himself; publicly credited as television’s originator only in 1928	Vol 3
John Logie Baird	Built the first working television system (1925), gave the first public demonstration (1926), and sold the Televisor commercially from 1930	Vol 5, Vol 6
Charles Francis Jenkins	American rival; built the Radiovisor/Radiovision system, demonstrating silhouette images from June 1925	Vol 7
Dénes von Mihály	Hungarian/German rival; built the Telehor system, publicly demonstrated 1928 and 1931	Vol 7
Boris Rosing	Russian pioneer; combined a mechanical mirror-drum transmitter with an early CRT receiver (1911)	Vol 7
Kenjiro Takayanagi	Japanese pioneer; demonstrated a Nipkow-disc-transmitter/CRT-receiver hybrid (1926), “the father of Japanese television”	Vol 7
Max Dieckmann / Rudolf Hell	German engineers working on an electronic (not mechanical) CRT system in 1925 — the boundary case that must not be counted among the Nipkow-disc pioneers	Vol 7
Philo Farnsworth	American inventor of the first fully electronic camera tube (image dissector), 1927	Vol 10
Vladimir Zworykin	RCA engineer; developed the iconoscope camera tube (patent filed 1923, working model 1933)	Vol 10
Isaac Shoenberg	Led EMI’s television research group; directed the programme that produced the Emitron tube and the winning 405-line system	Vol 10
Alan Blumlein	EMI engineer; contributed to the 405-line system’s scanning and signal-processing circuitry	Vol 10
David Sarnoff	RCA president; backed Zworykin’s iconoscope development at scale	Vol 10
Donald McLean	Forensically recovered Baird’s Phonovision discs (from 1982; publishable results by the 1990s); later built an NBTV digital standard converter (1988)	Vol 8, Vol 11
Doug Pitt	NBTVA co-founder; proposed the founding project and organised the 1975 meeting that formed the club	Vol 11
Stan Kujawinski	NBTVA co-founder; the club’s own documented source for why the modern standard settled on 32 lines rather than Baird’s 30	Vol 11
Chris Long	Australian schoolboy builder whose letter to Wireless World helped catalyse the informal circle that became the NBTVA	Vol 11

16.4 Museums & Collections

Science Museum Group (London) — holds original Baird apparatus from 1925–1930, including the Model C “Noah’s Ark” Televisor (c.1929, one of only ~20 built) and a Mervyn Unisphere mirror-drum television. https://collection.sciencemuseumgroup.org.uk/ (Vol 6, Vol 9, Vol 14)
National Science and Media Museum (Bradford, UK) — holds the surviving Telechrome tube and other Baird-related material. https://www.scienceandmediamuseum.org.uk/ (Vol 9, Vol 14)
Early Television Museum (Hilliard, Ohio, US) — a working restored Baird Televisor (serial no. 717), documented mirror-drum and mirror-screw specimens, and extensive online historical documentation. https://www.earlytelevision.org/ (Vol 7, Vol 14, Vol 15)
Museo Nazionale della Scienza e della Tecnologia Leonardo da Vinci (Milan, Italy) — holds a 1931 Fracarro aluminium Nipkow disc with documented square-section apertures. http://www.museoscienza.org/ (Vol 13)
Powerhouse Museum (Sydney, Australia) — holds a documented genuine Televisor specimen, part of the small population of surviving units outside the UK. (Vol 14)
The Narrow-Bandwidth Television Association (NBTVA) — not a museum in the institutional sense, but the living custodian of the scanning-disc tradition: an active international club with a quarterly Newsletter, an online forum, a Club Sales parts operation, and an annual Convention held in Loughborough, UK. http://www.nbtv.wyenet.co.uk/ (Vol 11)

16.5 Anchor Index

A topic-to-volume map for readers who arrived here looking for one specific thing.

Table 4 — Anchor Index

Topic	Volume(s)
Persistence of vision, selenium, earliest “telectroscope” proposals	Vol 2
Nipkow’s 1884 patent and disc geometry origins	Vol 3
Scanning theory, frame rate, flicker, bandwidth mathematics	Vol 4
Baird’s biography and first demonstrations (1925–26)	Vol 5
Televisor hardware: disc, motor, neon lamp, framing/phasing controls	Vol 6
30-line standard parameters (as implemented in the Televisor)	Vol 6, Vol 16
Rivals: Jenkins, Mihály, Rosing, Takayanagi, Dieckmann/Hell	Vol 7
Fernseh AG and Soviet mechanical television	Vol 7
BBC 30-line broadcast era (1929–35)	Vol 8
Phonovision and Donald McLean’s recovery work	Vol 8
Colour, stereoscopic, and large-screen television (Scophony)	Vol 9
Intermediate-film television	Vol 9
Telechrome (electronic colour CRT)	Vol 9
The Alexandra Palace trial and the 1937 decision	Vol 10
EMI, Emitron, Shoenberg, Blumlein, Farnsworth, Zworykin	Vol 10
NBTVA founding, history, and why 32 lines	Vol 11
NBTV signal structure: sync, bandwidth, encode-to-display chain	Vol 12
Disc geometry, optics, materials, motors, tolerances	Vol 13
Acquiring a genuine or modern set: market prices, authenticity	Vol 14
Restoration, building from scratch, safety	Vol 15
Glossary, standards table, timeline, key figures, this index	Vol 16
Building and driving the MindSets NBTV kit, the steampunk cabinet	Televisor Kit Build dive (companion site)

16.6 Cross-References

The full standards table above draws its numbers from the Baird 30-line hardware described in Vol 6 — Inside the Baird Televisor and the modern NBTV signal described in Vol 12 — The NBTV Signal Explained; neither volume should ever be found stating a different figure for the same parameter.
The people listed in Key Figures are introduced in fuller biographical and technical detail in Vol 3 — Nipkow’s Disc (1884), Vol 5 — John Logie Baird & the First Television, Vol 7 — The Rivals, Vol 10 — Why Electronic TV Won, and Vol 11 — The Modern Revival: NBTV and the NBTVA.
The museums and collections listed above are the same institutions cited throughout Vol 6, Vol 9, Vol 13, and Vol 14 — Acquiring a Mechanical Television.
Every date on the timeline is drawn from, and should agree with, the corresponding body volume named beside it — this volume introduces no new dates of its own.
The companion Televisor Kit Build dive on this site picks up where this series’ theory and history leave off: assembling the MindSets Online NBTV kit, feeding it a signal, and building its steampunk cabinet.
For the complete narrative arc this reference volume compresses, start from Vol 1 — Introduction & Orientation.