ZETRON 025-9581M, Installation And Maintenance Manual

Page: 22 / 196

System Overview
22 025-9581M
Communication Interface
The Station Transponder Units are designed to operate over a private IP network. All
commands traveling out to the stations and all station/units status messages going back to
the FSA Server are handled over the IP network. Each Station Transponder Unit in the
system is assigned a unique IP address so that FSA Server can communicate with it.
Audio traffic can be sent over the same network using VoIP software and hardware, or it
can be sent by means of either conventional or trunked radio systems. When VoIP is used,
there will be a single VoIP intercom card at each station location even if there is more than
one Station Transponder Unit installed there. Each VoIP intercom card is assigned a
unique IP address.
The Station Transponder Unit receive interface includes a 4-wire, transformer coupled,
audio input with adjustable sensitivity. Input impedance is jumper selectable to either
600
Ω or 10 k Ω .
The Station Transponder Unit transmit interface includes a transformer coupled audio
output with adjustable output levels. The Model 6203/6204 can transmit either FFSK
modulated data packets for Model 26 backup or voice over the radio.
Conventional Radio Interface
Besides the transmit and receive audio connections, the Station Transponder Unit provides
an open drain, Push-to-Talk (PTT) output signal for transmitter keying and a Carrier
Operated Relay (COR) input for detecting channel availability. If the radio does not
provide a COR output signal, the Station Transponder Unit has an internal VOX circuit
(with adjustable sensitivity) for detecting channel activity. Along with these special
hardware circuits, there are a number of user-configurable software parameters for setting
up and optimizing the radio interface.
Trunked Radio Interface
When used only to support voice communications in an FSA system, the Station
Transponder Unit will be connected to a trunked radio in the same way it is connected to a
conventional radio. The only difference in operation is that the user will press and release
the PTT button on the handset and listen for the trunking go-ahead prompt before pressing
PTT and speaking. If the trunking radio is being used to support a Model 26 being used as
backup then the following applies.
When used with trunked radio equipment, the Station Transponder Unit alters the
designation of its inputs and outputs. The Station Transponder Unit provides an open drain
Channel Request signal (the PTT connection) and a Channel Grant input (the COR
connection). The software in the Station Transponder Unit responds to these signals in a
manner that is consistent with the differences between conventional and trunked radio
operation. When configured as Trunking interface, the Station Transponder Unit interprets
the COR input as an “OK to transmit” signal rather than a “channel is busy” signal. Along
with these special hardware circuits, there are a number of user-configurable software
parameters for setting up and optimizing this interface.