DID TEURS

Photo B. The S2A speech synthesizer board from Te/esensory
Systems, Inc. The large Ie is the CRC micro-cccuotler.
The entire 24-word vocabulary is contained in the smaller
16K ROM. All connections are by way of the double-sided
card edge connector (10 pins per side).
work. But, recogn izing potential
need for a specific
multiplex rate, the designe
rs at lSI allowed provision
for user control of the multiplex
rate on the l SI 7031
counter Ie. By removing
t he capacitor normally
u sed for t he o n-board
clock, it is possible to control
the sca n oscillator in
the chip.
A Scan Reset pin is provided,
which advances the
sca n counter in the IC to the
left-ha nd digit- Th is pin
could be used to reset the
scan counter, but it wasn't
found to be necessary.
However, by applying a
pulse to pin 39, the scan inpu
t, the counter IC would
step across t he display, left
to right, just as was desi red!
The actual interface is
very simple, consisting of
just one 4D-cent CMOS gate
package in addition to power
supply and a udio amplifier
parts (see Fig. 1). The
speech readout is initiated
by pressing the Speak
switch, which sets an R-$
flip-flop a nd allows the
st robe line to go true. There
will be a short pulse when
the Busy line signals the
end of the word, and this
acts as a c lock pulse to
move the scan counte r in
the counter Ie on to the
next digit.
The process continues
until the last digit is spoke n.
when the pos itive edge
from the eighth counte r
digit serves to reset the flipflop
a nd term ina te the
speech. The only connections
required to the counter
a re the four BC D data
lines, the addition of a
switch to the scan input to
se lect visual or audible drsplay.
and a wire to the
eighth digit strobe. Because
of the ease of interfacing
this circuit, it should be
eas ily d u p licate d, a nd
TSI Model S2A Synthesizer
Vocabulary list
Data Code Word
(Octal)
000
001
002
003
004
005
006
007
01 0
011
012
013
0 14
0'5
01.
017
020
021
022
023
02'
025
02.
027
030
Oh
One
Two
Three
Four
Five
Six
Seven
Eight
Nine
Itmes.Mtnus
Equa ls
Percent
Not used
Low
Over
Root
Em
Times
Point
Overflow
Minus
Plus
Clear
Swap
Photo C. Inside the counter. The speech board is visible on the feft and the power supply
andamplifier-interface circuit board are on the right. Note D IP-plug connections to counter
mainframe. Large modufe at right is dddc converter that generates -10 vo lts fo r synthesizer.
Speaker is mounted to top cover.
Table 1. The " voice" o f the
S2A is that of Dr. Forres t
Mozer, inventor of the
speech-generation afgorithm
used by the LSI controlfer.
The speech synthesizer
is a static-sensitive device
and normal MaS handling
precautions should be
observed.
54 73 Magazine· April, 1981