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Chapter 6 - Introduction to Wireless Intercom Systems 87
Figure 6.1
The first beltpack based wireless intercom system.
Each user station in the system consisted of two beltpacks, one for transmit and one for
receive. Two beltpacks were necessary to combat the phenomenon know as desensing,
where a transmitter in close proximity to a receiver causes the receiver to have greatly
reduced sensitivity. Desensing is discussed in greater detail in a future section. Each
wireless user’s transmitter was on a unique frequency which corresponded to their own
receiver in the base station. All of the wireless users’ receivers were tuned to the same
frequency which corresponded to the single base transmitter. A single headset with a split
feed cable eliminated the need for an external headset interface box. See Figure 6.1. By
utilizing this system, each wireless user could communicate to both hardwired and
wireless intercom users in a full duplex mode.
This system, at long last, provided engineers with a reliable and functional solution to the
wireless communications problem. Future systems would combine the transmit and
receive beltpacks and incorporate numerous interfacing and operational advantages. We
look at some of these in the next section.
Modern Day Wireless Intercoms
Today’s wireless intercom systems are technological giants compared to their earlier
predecessors. They allow users to “cut the cable” of hardwired party-line systems and
move about freely within the system’s operational range. Modern wireless intercoms can
be either party-line intercom systems or individual beltpack systems that allow users to
operate independently from other wireless users. Good quality systems can be seamlessly
attached to existing hardwired communications systems commonly used in broadcast and
other facilities. As discussed previously, modern, high quality wireless intercoms offer a
distinct advantage over traditional, two-way radios in that they offer a more natural full-
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