Product manual

Front Panel Expansion
13
Front Panel Expansion
Up to three expansion panels can be added to a Model 26 giving a total of 240 buttons
and 480 LEDs. There may also be up to 15 different dispatch positions. Each position is
operationally identical to the Master Position.
Figure 1 shows the relationship of the
various units in an expanded system.
Communication Interface
The Model 26 is designed to communicate with Model 6 Transponders via a voice band
audio communications path. This path must be capable of carrying audio signals between
300 Hz and 3 kHz (no DC signaling is used). There are user configurable, software
parameters for selecting the type of communication interface and for optimizing system
performance for Wire Line, Conventional Radio and Trunked Radio systems.
The receiver interface includes either a 2-wire or a 4-wire transformer coupled audio
input with adjustable sensitivity. Input impedance is jumper selectable as 600 Ω or
10 kΩ.
The transmitter interface includes a transformer-coupled audio output with adjustable
levels. The Model 26 transmits FFSK data packets, signal audio and voice.
Wire Line Interface
The Model 26 requires the following wire line characteristics to successfully
communicate with a remote Model 6:
Parameter Description
Pass band Voice band (300 to 3000 Hz)
Freq. Response ±10 dB max over voice band, reference to 1 kHz
+1/–3 dB max over range 1200 to 1800 Hz
reference to 1 kHz
Maximum Loss End-to-end < 25 dB
Optimal loss = 6 dB
Impedance 600Ω to 900Ω
Balance > 50 dB longitudinal