Table of Contents
Advertisement
Theory of Operation
Overview
Revision D
UPPER LEVEL ASSEMBLY: Theory of Operation
This theory of operation is written for APEX telemetry transmitter
assemblies pn 418793-001/002/003/004 using the schematic diagram of
the transmitter PCB, pn 801278-001/002/004, found in Chapter 7,
"Transmitter PCB."
The APEX telemetry transmitter acquires three differential leads of ECG
information and a pace channel from the patient and converts this
information to 10-bit NRZI digital data. This digital data is then
transmitted to a central receiving unit by phase modulating a carrier
signal. The RF carrier signal is broadcast using the patient leadwires as
an antenna.
The transmitter automatically powers up when two AA batteries are
installed into its battery compartment. Patient data is transmitted until
the batteries are removed, or are depleted.
Two switches are provided on the front of the transmitter for requesting
a central station data graph, verifying lead status, and for de-activating
the visual and audible alarms at the central station unit. There are no
other user accessible features on the transmitter.
The transmitter PCB contains all ECG signal acquisition circuitry, the
pace detect circuitry, the microprocessor and A/D converter support
circuitry, and the RF circuitry.
•
The ECG circuitry includes a reconfigurable front end, ECG detect,
and pace detect circuits. The front end circuitry has a three-stage
ECG section and pace detect section with the first two stages being
common to both.
•
The digital circuitry is composed of the microprocessor, an A/D
converter, and supporting circuitry.
•
The RF circuitry includes the frequency synthesis circuitry and the
BPSK phase modulation circuitry.
APEX Telemetry Transmitter
401566-166
6-3
Advertisement
Table of Contents
