6
signal which the equipment may receive in the operational installation.
This will often be loud, close talking into a microphone. It should be pointed
out here that background hum and noise from equipment earlier in the
chain, such as a sound or TV system may sound very troublesome when
subjected to some 20-36db extra amplification. When this occurs, the gain
must be kept at a lower, acceptable level. Where the dominant signal is
music, then it may be important to keep the compression level low, to
prevent serious degradation of the music dynamics. Experience will
indicate which level to use.
REMEMBER: once the DRIVE control has been set, only adjust the GAIN
control, as otherwise the correct operation of the equipment is impaired.
To adjust the VOX switching level, set up the equipment with the switches
in the desired configuration, with Microphone 1 control at minimum. Set up
the equipment for correct signal levels on the other inputs. Increase the
setting of Microphone 1 until the desired input signal level operates the
VOX switching, and the output signal from this input is correct. A typical
application for this could be with the microphone fixed to the side of a
telephone, so that the ringing will trip the switching, while the normal
background noise is suppressed.
7. GENERAL INFORMATION
7.1 Difficulties
If you have any difficulties in calculating the loop design, or experience
difficulties with the operation of the equipment, then contact your supplier
or Ampetronic Ltd. It is useful to have all the relevant data available when
contacting our technical staff who will be pleased to help you. The following
are known trouble areas:
– Strong hum field, mainly from fluorescent light fittings, or electrical wiring
where current flow and return are not in the same cable or duct
– Loop cable installed in a manner where it is in close proximity to
microphone (or other audio) cables for an appreciable length. Telephone
cabling can also be very sensitive to this coupling.