GE Medical Systems Corometrics 340, Service Manual, Page: 62 / 82

5-10 Model 340 Telemetry System Revision A
2006920-001
Calibration: Receiver Calibration
Mode Outputs
1. The mode output signals are generated via open collector transistor
switches in U2. For test purposes, the outputs must be connected to a
fetal monitor via the US, ECG and UA interconnect cables or pulled
up to +5 V (TP5) by 10k
Ω
resistors.
127(
When testing the TOCO and IUP mode outputs, the receiver
front panel UA mode switch must be in the appropriate
position.
2. Refer to Table 5-3. Confirm operation of U2’s internal open collector
transistor switches. Correct operation is a closure to ground at the
connector pins indicated. The transistor switch will be open if either
control signal is high.
Pulsed Doppler Ultrasound Audio Converter
1. Feed a 1 Vp-p 300 ms burst of 300 Hz sine wave into J6 pin 2 (with
J6 pin 6 as reference); observe the waveform and its envelope at
TP14. Adjust the signal generator for an amplitude of 1.0 Vp-p at
TP14. With J201 pin 8 open, confirm the waveform at TP43
maintains the same envelope shape, but at half the frequency (150
Hz) as the signal at TP14. Confirm the peak-to-peak amplitude at
TP43 is equal to the amplitude at TP14 –0 + 0.6Vp-p.
2. Connect J201 pin 8 to ground and observe the waveforms at TP14
and TP43 are the same.
Table 5-5. Open Collector Transistor Switch Testing
Signal Name Control Signals Reference Points UA Mode Switch
USEN* TP1 and TP7 Low J201-11 and J10-12 —
MECGEN* TP1 and TP31 Low J202-4 and J10-10 —
FECGEN* TP1 and TP30 Low J202-2 and J10-3 Low —
TOCOEN* TP1 and TP5 Low J203-12 and J10-11 TOCO
IUPEN* TP1 and TP5 Low J203-11 and J10-13 IUP