ConwayLife.com

At Elementary conduit is the start of a GoL alphabet of particles.

B - B-heptomino
C - century / bookend
D - dove
E - E-heptomino
G - glider
H - Herschel (not J)
L - LWSS
M - MWSS
P - pi-heptomino
Q - queen bee
R - R-pentomino
SE - Switch engine
T - T-tetromino
W - wing

Are there other important items for this alphabet?

At The Hunting of the Elementary Conduits it looks like the important letters are BCDHLMPQRW or G.

E (http://www.conwaylife.com/wiki/E-heptomino)
maybe

But there is the general problem that we have HWSS, LOM, HF, TL - so longer strings.

The switch engine is abbreviated as SE (http://www.conwaylife.com/wiki/SE), see also http://www.conwaylife.com/wiki/S.

T stands for t-tetromino, and thus by extension, traffic light.

Honey farm can be abbreviated to HF.

We have a lot of these 2-letter abbreviations, don’t we.

Rather than ask there, I'll ask here.

Is the reason the Switch Engine got left out of the Conduit database because:
1. Known Switch Engine converters aren't useful enough

The bobsled run is known, but it also mentions simpler converters are known.

EdPeggJr wrote:Is the reason the Switch Engine got left out of the Conduit database because:
1. Known Switch Engine converters aren't useful enough

Right. Most of the signals in what this thread calls the "GoL Alphabet" have elementary conduits that convert them to and from other signals. That is, for any signal type X that is listed in the Elementary Conduits collection, there will be both X-to-Y and Z-to-X elementary converters, for some other Y and Z signals in the Alphabet.

For switch engines, the only converters that have been found so far are highly engineered composite mechanisms -- except the bobsled run, but you can't use that to escape from switch-engine signals into other signal types.

EddPeggJr wrote:The bobsled run is known, but it also mentions simpler converters are known.

Where do you see the mention of simpler converters? Glider-to-switch-engine, Herschel-to-switch-engine, etc. have definitely gotten simpler, but they still require splitting one signal into multiple precisely timed signals -- definitely not elementary.