Nellcor N-200 Operator's Manual page 59

For example, if the monitor status byte is ASCII 015, (binary
00001111), this means that the monitor is locked on pulse,
sensor attached, audio alarms enabled, and ECG not in use.
T = Time hhmmss
Q = High Saturation Alarm Limit
n = ASCII character, normally a number
<CRLF> = Carriage Return and Line Feed
<CHKSM> = 1 Byte Binary Checksum (uncoded)
Conversation Format
In this mode, the output is a single parameter, sent by request
only. For example, the computer requests the current pulse
rate by sending an R. The interface responds with
STX/Rnnn/CR/LF where (nnn is the pulse rate). Other request
codes are listed in the preceding section.
Conversation Format is available for all monitor parameters.
N-9000 Recorder Format
This mode is used to communicate with a NELLCOR N-9000
recorder/interface.
Beat-to-Beat Format
This mode transmits saturation and pulse rate data once per
beat in the following format:
STXRnnnSnnnCRLF
Trend and Event Command Format: The following
information describes the data that will be sent to and received
from the N-200. The monitor responds to these commands in
any of the six ASCII modes. Common parameters in these
expressions are:
Text Marker Hexadecimal Meaning of Marker
< STX >
< ETX >
< CRLF >
N-200 data packets are described later in this section.
02H Start of transmission (text)
03H End of transmission (text)
0DH, 0AH Carriage return and line feed
Guide to Operation
53