Figure 4.7 Typical Keypanel
Typical User Station
(Keypanel)
+8 dBu Audio From Matrix (Listen)
Speaker |
|
| Serial | Rs485 Data |
|
| CPU | ||
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| Data | To Matrix | |
|
|
| ||
Headset |
|
|
|
|
Microphone | Switches | Indicators |
|
|
|
| + 8 dBu Audio | ||
|
|
|
| |
|
|
|
| To Matrix |
|
|
|
| (Talk) |
Normally, a user station provided by the manufacturer of the intercom performs all of these functions. However, suppose the user requires a user station to be very small, low cost, and mounted in a single gang electrical box, and that the station only needs to call a security desk. The user, dealer, system contractor, or any third party company can build a small box with a microphone, preamplifier, audio amplifier, speaker, and a push button. The only question is, how does the builder easily create the control protocol to notify the matrix that he or she wishes to be heard? Making the situation more difficult is the fact that manufacturers do not publish the details of their control protocols.
The answer is simple. The push button of the user station is connected to a logic input of the matrix (the “I” in GPI/O) and the operating software is instructed to treat the activation of that logic input as the press of a talk key
Figure 4.8 Simplified Low-Cost User Station
Single Gang
Electrical Box
“Vertical”
Speaker
MIC
CALL
+8 dBu Audio From Matrix
Simple One Button User Station
Microphone
+ 8 dBu Audio
To Matrix
CALL
Switch
Contact Closure to
Matrix GPI Input
Speaker
A number of other examples with more detail of GPI/O are shown in the next chapter.
More Complex Ancillary Functions
The examples above presume that the interface requirements are very basic, and can be defined as an action which controls or is controlled by a single change in one logical state, a single “bit” of binary information.
There are often cases where the definition is nearly as easy, but multiple conditions must be met. Perhaps, in the previous security desk example, the user needs a certain intercom panel to call the receptionist from 8:30 AM until 4:30 PM, then from 4:30 PM until midnight calls the security desk, and then from Midnight to 8:30 AM sends the signal through the building paging system to wake up the watchman.
Another example, if the “ON AIR” light in studio three is on, DO NOT allow audio to go to the three speaker stations in studio three, unless the panels are feeding headsets AND NOT the built in speakers.
In RTS™ Zeus™,
C h a p t e r 4 - I n t r o d u c t i o n t o M a t r i x I n t e r c o m S y s t e m s 55
