User guide
Doortello Business
Issue 1.00
Page 12
Line impedance
DB Bus
The DB bus connectors is used to connect the different modules of the door station
system to the door phone using a flat cable.
Volume adjustment
On the Doortello Business you can adjust the volume of the microphone and the
loudspeaker. If the volume of the loudspeaker is not high enough you can enhance
this by powering the unit (read also the chapter
External DC power supply
for
more information).
Please note!
Without an external power supply it can happen that with very high
loudspeaker volume and noises (i.e. feed back noise) the telephone line
current not enough is to support the module. In this case the device will
automatically reduce the loudspeaker volume.
For a better sound quality of the speaker phone you need a perfect line impedance
adaptation. The line impedance jumpers is therefore available to select the
impedance of the telephone line you are using. You can choice between 600 Ohm
(default) and Zr line impedance. Which type of line impedance you can normally be
read in the technical documentation of the telephone switch or adapter you are
using. Normally small switches and adapter have 600 Ohm, large switches and
public telephone line (in Europe) have Zr. IF you are not sure which lien impedance
you have just use the selection which gives you the best results.
line is used, a larger capacitor has be installed. This capacitor has to loaded at
the first activation of the device. As the processor can not work until this
capacitor is loaded the unit will take some time as only the idle current of the
telephone line can be used. This is only a few µA and it will take some
minutes time to load the capacitor. If you want to shorten this time you have
to call the device. Please read the chapter
First activation
for more details.
Please take care that some feature may differ if the unit is externally powered or
not.
Automatic heating element
If the device is externally powered an automatic integrated heating element will be
activated. This is used to ensure a correct functionality with outside temperature
down to - 20°C. The heating element is activated automatically at +10°C and will be
deactivated at +20°C.
