Vibratese is a system of information transmission based on time and intensity modulated signals. The first Vibratese devices, developed by F. A. Geldard in 1957, were constructed of five vibrating modules attached to the interpreter's chest. Each vibrator was responsible for a different segment of the script, with the duration and intensity of the vibration corresponding to a particular symbol.[1]
Vibratese was initially developed as a potential avenue to transmit intelligence to military targets in compromising environments.[1][2][3] While not touched upon in Geldard's first paper, its potential application for the deaf and visually impaired was understood.[3][4]
Geldard identified three tactile dimensions that could be easily and quickly discerned by an interpreter: duration, intensity, and location. Morse code is an example of an auditory system which transmits information modulated by duration alone, and can be used in a tactile device. Geldard found that utilizing all of these dimensions, instead of just one, allowed for higher information transmission rates. Several device configurations were identified as possible, including a seven point arrangement, but five was deemed sufficient. Geldard determined that three durations of signal (100 ms, 300 ms, 500 ms), and three intensities of vibration per vibrator was a viable system, and allowed for 45 symbols to be encoded using the five vibrators. Individual symbols were spaced 50 ms apart with a 100 ms pause between words. This allowed for a theoretical maximum transmission rate of 67 words per minute, versus Morse code with about 30.[1]
To prevent ambiguity each vowel character was assigned to a separate vibrating module. To improve speed, numerals were assigned to the longest duration signals and the remaining letters were assigned according to frequency. Several of the symbol slots were assigned to common English words.[1]
Vibratese symbol arrangement
Location
Duration
Intensity
Symbol
Upper left
short
high
O
Upper left
medium
high
B
Upper left
long
high
8
Upper left
short
medium
S
Upper left
medium
medium
of
Upper left
long
medium
Upper left
short
low
L
Upper left
medium
low
K
Upper left
long
low
7
Upper right
short
high
E
Upper right
medium
high
J
Upper right
long
high
2
Upper right
short
medium
P
Upper right
medium
medium
the
Upper right
long
medium
Upper right
short
low
T
Upper right
medium
low
V
Upper right
long
low
1
Middle
short
high
V
Middle
medium
high
Z
Middle
long
high
6
Middle
short
medium
F
Middle
medium
medium
X
Middle
long
medium
Middle
short
low
H
Middle
medium
low
Q
Middle
long
low
5
Lower left
short
high
I
Lower left
medium
high
G
Lower left
long
high
0
Lower left
short
medium
C
Lower left
medium
medium
in
Lower left
long
medium
Lower left
short
low
R
Lower left
medium
low
W
Lower left
long
low
9
Lower right
short
high
A
Lower right
medium
high
M
Lower right
long
high
4
Lower right
short
medium
D
Lower right
medium
medium
and
Lower right
long
medium
Lower right
short
low
N
Lower right
medium
low
Y
Lower right
long
low
3
Several issues were identified with the system. The amount of training time required was seen as excessive. It was stated that 30 lessons, equated as hours, was required to learn the system.[3][4] Additionally, ambiguity along the short-time intensity axis was an issue. A solution offered was to add an additional time duration, while decreasing the intensity axis.[1] Additionally, Geldard proposed a potential system using closely spaced vibrators which could transmit focal movements, like the tracing of a finger, on the subject. Such a system could be used like a Lorm alphabet.
