3M C960, Service Information

Page: 10 / 158

Model C960 Headset Intercom System
OperationandDiagrams
1-3
E
3M 2000 May
The headset receives microphone audio signals from
the base station on frequency B and transmits both
audio signals and control tones on frequency A . The
control tones are above the audible range, and
function to turn the base station receiver ON to enable
reception of the audio signal from the headset
microphone. Because the control tones are above the
audible range, audible tones from devices such as
telephones, pagers, and radios will not interfere.
The base station transmits on
frequency B and
receives on frequency A . The receiver in the base
station operates above the audible frequency range.
While it receives the high-frequency control tones
from the headset, it is not affected by audible tones
from devices such as telephones, pages, and radios.
The transmitter in the base station is always
transmitting a “no signal” transmitter carrier, even
when there is no microphone audio from the menu
sign or headset operator being broadcast. This “no
signal“carrier iscontinually broadcastto andreceived
by all headset receivers. It serves to block out other
radio-frequency signals or noises from headset
receivers.
Similarly, the headset receiver is always ON to enable
the listen mode. The headset transmitter turns ON
only when a talk or page switch is pressed.
In standard communication systems, the output from
the headset receiver is muted when the headset
transmitter is ON. This provides standard
communication (talk
or listen).
In duplex communication systems, the output from
the headset receiver is enabled (not muted) when the
headset transmitter is ON. This provides duplex
communication ( simultaneous talk and listen).
The two sets of transmitters and receivers work
togethertoprovide audiocommunication betweenthe
customer at the menu sign and the headset operators
inside the drive-through restaurant or between two or
more headset operators.
All audio transmitted by a headset during talk
operation is heard by:
S
Menu sign customers.
S
Personnel wearing active headsets.
S
People near the optional monitor speaker.
All audio from the menu sign is heard by:
S
Personnel wearing headsets that are operating in
the talk/listen mode.
S
People near the optional monitor speaker.
Talk/Listen Communication
Headset to Menu Sign
After the vehicle detection signal is presented to the
base station, the base station broadcasts a repeating
alert tone to all active headsets.
The headset operator presses and holds the talkbutton
to acknowledge the customer at the menu sign and
cancel the alert tone. When the headset operator
speaks into the microphone, the headset generates a
talk control tone and adds it to the microphone audio.
The microphone audio and talk control tone are then
transmitted to the base station. The talk control tone
turns the base station receiver ON , enabling it to
receive the microphone audio.
n
Note
The talk control tone is above the audible
frequency range, and is used to prevent the base
station receiver from receiving signals from other
devices (telephones, pagers, etc.) that might be on
the same frequency.
When the base station receives the microphone audio
signal, it re-transmits it to all headset receivers. The
same microphone audio signal is also routed to the
menu speaker amplifier and the monitor speaker
amplifier.
The menu speaker amplifier routes the amplified
microphone audio through wire to the menu speaker
where it can be heard by the customer. The monitor
speaker amplifier routes the amplified microphone
audio through wire to an optional monitor speaker
(typically located in the kitchen area) where it can be
heard by anyone in close proximity to the speaker.
n
Note
The menu sign audio is not turned ON unless the
base station receives a talk control tone from the
headset. However, the the monitor amplifier is
always turned ON.