T4 EEG Amplifier User Manual
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Both Bluetooth and WiFi technologies, however, use sophisticated error detection and error correc-
tion techniques to deliver correct data. Additionally, if a transmission cannot be decoded due to in-
terference, the transmission is resent. This interference will, of course, increase as the number of
coexistent devices in proximity to each other increases. Due to the robust error detection mecha-
nisms, however, as the interference level increases, data continues to be delivered correctly, but
the data rate decreases as the number of dropped packets increases.
In terms of security, both system use authentication with encryption and pin codes/pass words. In
addition, the T4 itself uses a proprietary Interface Protocol thus preventing a non-authorised user
from taking control of the device.
When transmitting wirelessly, data packages are time-stamped when acquired by the amplifier, be-
fore being transmitted, and when received by the application they are recorded according to this
timestamp. In this way, there is no risk associated with delayed communications or missing data
packets over a wireless link since, if the recording software detects missing packages, an event is
inserted into the recording to notify the operator. In the extreme case whereby the interference
causes the wireless link to be dropped all together, the application automatically reconnects when
the interference is removed.
Quality of Service and Associated Risks
1.
The risk of corrupt data due to interference is very small due to error detection, error cor-
rection and resend data packet mechanisms. In addition to this error detection and correc-
tion, the application provides time-stamped data packages, which enables the detection of
corrupt, delayed or missing data.
2.
The risk of missing data due to interference is also very small, but at the extreme, the data
rate decreases as more and more data packets have to be dropped and resent. Ultimately,
in the presence of extreme interference, the data rate will decrease to zero and the wire-
less link will be dropped. This situation is also adequately handled with the provision of
time-coded data packets, which enables the detection of corrupt, delayed or missing data.
In the extreme case whereby the interference causes the wireless link to be dropped all to-
gether, the application automatically reconnects when the interference is removed. This sit-
uation is very similar to being out-of-range and the same mechanisms apply and, again,
the application will automatically reconnect when the device comes back into range.
In the presence of extreme and persistent interference, the cabled USB connection is, of
course, available.
3.
The risk of unauthorised users is very small due to the authentication requirements of the
wireless link and the fact that the T4 Interface Protocol is proprietary.
4.
The medical system uses mature, industry-standard hardware and protocols: Bluetooth and
WiFi. This ensures that the system utilises all the benefits associated with these mature
standards, concerning the authentication, data integrity and interference performance as
discussed in this document.
5.
The radio modules are tested according to their own EMC emissions and immunity stand-
ards: EN 300 328, EN 301 489-1, EN 301 489-17 and IEC 60601-1-2 (Bluetooth).
6.
The radio modules are pre-certified and Type Approved.
Considering the medical system function, its indication for use and very low risk associated with
a low level of concern, the analysis, evaluation and preventative measures undertaken reveal
the low risk associated with wireless communication. In the presence of extreme interference,
the rate of delivery of data packets will decrease until ultimately, the wireless link is dropped.
Wireless communication problems are identified, prevented and mitigated, as described. The
application identifies these wireless problems and automatically reinstates the wireless link if
dropped in the presence of extreme interference. Alternatively, the cabled USB connection is
available.
Pre-compliant Wireless Modules
The use of pre-compliant, certified and Type-approved optionally-fitted internal Bluetooth and WiFi
wireless modules which comply with applicable national radio regulations ensures best perfor-
mance, interoperability, coexistence and quality of service is achieved.
Specifications (taken from Appendix 1).
Bluetooth Module
Specifications: