MEDISWITCH®
Rehab and Care Technology
Instruction Manual
VarioFon noise detecting unit
Nurse call and personal transmitter technologies
rehab and care technologies
Lehmann Electronic GmbH Niederkassel
Information on Electrical Connections for the Version with Open Cable Ends:
Assignment of the version without power supply
unit
Assignment of the version with power supply
unit
Power supply connection +Ub
Power supply connection 0 V
Relay –potential-free centre contact (m)
Relay –potential-free centre contact (m)
Relay –potential-free NO contact (a)
Relay –potential-free NO contact (a)
Relay –potential-free NC contact (r)
Relay –potential-free NC contact (r)
BL input - reassurance light 0 V 20 mA max.
BL input (1) - reassurance light 0 V
BL input (2) - reassurance light +24 V/12 V 20 mA max.
Additional Information on Operation
Microphone Control:
The device comprises an electret microphone. At maximum sensitivity it can correctly detect any room noise within a distance of 4 to
5 metres.
If the device is placed in the vicinity of a patient, amplification should only slightly be increased.
Noise Filter:
The device should not permanently trigger false alarms during radio / TV usage or normal conversations, for example.
Use the “noise filter” control to adjust the basic noise level.
The noise level can be adjusted in seven not exactly linear steps using the rotary knob and the LED indicators according to table 2 on
page 2 of this instruction manual.
At the same time, the noise recognition detection time changes proportionally with noise level.
The purpose is as follows:
First example - in the case of a “normal” room situation, that is, when the TV/radio is not too loud and the talk volume is normal
(corresponding to a medium response characteristics), any noise up to this noise level will not result in a triggering.
A noise exceeding this preset noise level results in a call triggering only if it exceeds this basic level for a certain uninterrupted
period.
When a gunshot is fired on television or someone loudly places a food tray on the bedside table, this louder noise is too short to trigger
the alarm or stopped before the minimum period is exceeded, when coughing, for example.
Therefore, when medium response characteristics are selected, the patient should use a longer word as a call, that is, “nuuuurse” and
not simply “hello”, for example.
In most cases this “normal” setting with medium response characteristics is the best choice.
Sometimes, it seems as if that the sensitivity changes on its own.
The reason is as follows:
Usually, during the day there is a certain basic noise level that exceeds the set threshold value from time to time but usually not long
enough to trigger a call.
Therefore, triggering a call seems to require that the basic level and its noise peaks is exceeded for a longer time and at a higher
volume.
During the night the basic level is usually completely absent. Therefore, the evaluation unit can much more easily recognise a word or
a sound.
Loud snoring can be problematic since the evaluation unit cannot distinguish the loudness and the duration of the generated noises
from a deliberate call triggering.
Second example –maximum evaluation, rotary knob fully clockwise.
In this case the basic evaluation level is very low and at the same time the noise triggering time is reduced.
Then, in most cases a “hello” spoken in a quieter voice is sufficient to trigger a call.
