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MEDEA Installation Manual
2.2
Choosing the cables
2.2.1
RS485 Bus cable
Use a 4-conductor multi-core cable for the RS485 bus. The use of a twisted and shielded cable is
recommended. The conductors connecting the A and B data bus signals must have a minimum cross-
section of 0.22 mm
2
.
The shields can be connected to each other at the negative terminal of the control unit power supply.
If additional power supplies are used, the shields of the secondary buses can be connected to each other
at the negative pole of the supplementary power supply unit.
IMPORTANT
Never connect the cable shields to earth or to the side of the device. Connect from
the centre side only.
2.2.2
Cable for detectors and sirens
Use a 6-conductor shielded multi-core intrusion detection cable for the connection of detectors
(unbalanced connection) and wired sirens. The conductors connecting the inputs must have a minimum
cross-section area of 0.22 mm
2
. A cross-section area of 0.5 mm
2
is recommended for the power supply.
A 4-conductor cable can be used to connect detectors in balanced mode.
The shields can be connected to each other at the negative terminal of the control unit power supply.
If additional power supplies are used, the shields can be connected to each other at the negative pole of
the supplementary power supply unit.
IMPORTANT
Never connect the cable shields to earth or to the side of the device. Connect only to
the control unit side power negative.
2.2.3
Power conductor size
The conductor cross-section area must ensure that the supply voltage to the various devices is correct to
achieve stability, efficiency and interference immunity.
The most critical power supply situation for the system must be used to calculate the conductor cross-
section area, i.e. no mains power supply and back-up battery at minimum charge (11.5 V
⎓
). Under these
conditions, at full load, a voltage of at least 10.5 V
⎓
is present at the ends of all MEDEA system
components.
Therefore, the maximum permissible voltage drop on the power supply cables is 1.1 V
⎓
(= 11.5 V
⎓
– 10.5V
⎓
), i.e. 0.5 V
⎓
on the positive conductor and 0.5 V
⎓
on the negative conductor.
IMPORTANT
The minimum operating voltage of other devices used, such as IR detectors,
actuators, sirens, etc., may be higher than 10.5 V
⎓
. Check the data sheets of the various devices
for supply data and tolerances and make calculations based on these values, if higher.
Содержание MEDEA
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