Schiller AT-102, Service Handbook

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2.6
AT-102 Service Handbook
MK 18-1 Main Board (cont.)
ECG Signal
The incoming ECG signals RA, LA, and C1 to C6 are low-pass filtered and applied to non-
inverting operational-amplifiers giving a gain of 11. The signals are further band pass filtered
(approximately 0.05 Hz to 470Hz) and amplified by 23 before being applied to the
multiplexer.
The multiplexer sampling rate is 1000Hz.
Noise Damping
The right leg electrode to the patient is the signal ground reference signal. To assist in
cancelling some patient noise and thus reducing incoming signal distortion, the incoming
signal from the patient left leg electrode is phase shifted 180 o . This phase shifted signal is
then used by the signal ground reference to cancel (or reduce) patient induced noise.
RS-232 Interface
This is a standard RS-232 / V.24 interface connected to the MK 18-10 main board. The
communications controller contains a USART and interface circuit which performs the
parallel / serial and serial / parallel conversion for the transmission and reception of data
and provide signal level compatibility with RS-232 standard.
External Modem
An external modem can be connected to the RS-232 output from the AT-102 and be used
for transmitting memory contents over a telephone line.