PCM-2 Manual.pdf - Voss Associates

Voice Annunciator Option (PCM2 OPT2)
This option for the PCM-2 includes a Voice Annunciator PC Board and an audio
speaker. The Voice Annunciator speaks phrases which prompt the user for proper
body positioning for measurement, announce monitor status, and prompt data
input requirements. The Voice Annunciator is connected to the RS-485
communications bus and is controlled by the Front Panel Board. A volume
adjustment is included on the Voice Annunciator's PCB.
The Voice Annunciator PCB is mounted on the underside of the unit's CRT
mounting bracket in the upper electronics enclosure and its audio speaker mounts
adjacent to the PC speaker in a bracket in the ceiling of the unit.
Voice Annunciator
Board
General Description
Theory of Operation
The Voice Annunciator Board consists of an 80C5IFA microcontroller, a 27C256
EPROM containing the system program, a TMS50C20 speech synthisizer, a
27C5I2 EPROM containing the speech data, a low pass filter, a push-pull audio
amplifier and a set of configuration DIP switches. Reference 11534-D3I3, Voice
Annunciator Assembly Drawing for proper switch settings.
The Voice Annunciator Board will output a speech phrase based on data received
from a keypad through connector 14 or from the serial port (RS-485, RS-232, or
TTL level depending on configuration used) via connector 12. When the
microcontroller receives a phrase number to be spoken, it then latches the phrase
number to the speech synthesizer. The speech synthesizer then retrieves the
digitally stored data from the speech EPROM, AlO, converts it to the proper
format and outputs the data to the analog circuit.
The analog cicuit uses a low pass filter to remove the unwanted high frequency
signal from the true speech signal. The speech signal is then fed through a pushpull
audio amplifier to the speaker. The volume of the speaker output is set by
the potentiometer R14. Potentiometer RI8 acts to balance the two audio
amplifiers. RI8 must be adjusted until the voltage measured between pin 1 of
Al3 and pin 1 of A14 is 0.0 Vdc. Failure to do so will cause a constant DC
current flow through the speaker which will eventually cause permanent damage
to the speaker.
PCM2MANI REV AI Arril 1995
'17-11