Cloud Electronics CX122 - Manual (Page 4)

music signals via a fire alarm control panel in an alarm condition. The CX122 provides a facility
to attenuate the music signals, by using a fully floating (isolated) pair of contacts in the control
panel which would need to be closed during an alarm condition.
In the mute mode, a gain reduction of 20dB is effective on the music signals only. The
microphone channel automatically switches to the emergency mode and will operate on both
zone outputs irrespective of the routing, level control and VCA module settings. A pre-set
potentiometer (PR1) mounted on the PCB can be adjusted to give the required microphone
level in the emergency mode.
It should be noted that in order to avoid a panic situation, the music muting reduces the gain
over a period of approximately 10 seconds. The recovery is also subject to a similar delay.
General Notes
Earthing
The 0V rail on the CX122 is connected to the mains earth and the unit must be earthed. Under
no circumstances should the mains earth be disconnected to remedy earth loop hums. If a
mains powered signal source is used which is also earthed, then earth or ground loop hums
may cause problems. The 'hum' can be remedied in several ways. If a problem is caused by
the link to power amplifiers, using balanced connections with the cable screen only connected
at the receiving end may reduce the noise. Alternatively, re-route the mains supply of the
equipment to the same point as that of the CX122. (Note: Microphone cables must be earthed
at both ends).
Rack Mounting
The CX122 can be mounted in a standard 19" equipment rack and occupies 1U of space.
Avoid mounting the unit in close proximity to large power amplifiers which may radiate
substantial magnetic fields and heat. Earth loops may also cause problems when several units
are mounted on a common fixing rail. The use of insulating screw cups together with nylon
spacers can solve the problem.
SAFETY
CONSIDERATIONS
CAUTION - MAINS FUSE
To reduce the risk of fire, replace the mains fuse only with the same type, which must be a
class 3, 240 Volt, time delay type, rated at 50mA where the mains input voltage is set to 220-
240 Volts AC. For a mains voltage of 110-120 Volts AC, the fuse should be rated at 100mA.
The fuse body size is 20mm x 5mm.
CAUTION - SERVICING
This unit contains no user serviceable parts. Refer servicing to qualified service personnel. Do
not perform any servicing unless you are qualified to do so.
WARNING
To reduce the risk of fire or electric shock, do not expose this unit to rain or moisture.