SECTION 3 - BASIC OPERATION
The purpose of the RTT signal is to inhibit the sharing terminal when the
Model 16 wants to transmit. If the sharing terminal is transmitting when
the Model 16 asserts RTT, it can finish as normal and the Model 16 will
wait. When it finishes, it is inhibited from keying up again and the Model
16 takes control of the transmitter.
If both terminals want to transmit but are inhibited by a busy radio
channel, the RTT signal serves to prevent a race for key-up. As soon as the
busy channel inhibit clears, the Model 16 will take control because its RTT
is still providing a busy inhibit to the sharing terminal.
INHIBITS
Two inputs are constantly monitored to determine whether the Terminal will
be able to gain control of the transmitter and key it to broadcast. The
Channel Busy input indicates when the radio channel is available. The
Terminal Busy input indicates when another paging terminal has control of
the transmitter. If either input is asserted the front panel "Busy" LED
lights and the Model 16 will be prevented from keying PTT. As soon as BOTH
inputs are cleared, the Terminal extinguishes the "Busy" light and starts a
timer for the period of the programmed Channel Busy time. Only if both
inputs remain clear for the full period will the Terminal be able to key
up. If either input is asserted during the Channel Busy time the "Busy"
light is relit and the timer is started over.
KEYING
The Keying operation consists of setting the relays to their appropriate
positions and lighting the "Transmit" LED. The Push to Talk (PTT) relay
switches to the closed position and provides the signal to turn the
transmitter on.
Also included within the PTT relay is a set of contact to isolate the
digital data output line if need for transmitter sharing.
The Key Up Delay time is a programmable value that determines the length of
the pause between PTT activation and the transmission of paging data. The
Key Up Delay gives the transmitter any needed time to come up to power.
PAGING
It is during the Paging operation that the actual digital paging
information is sent. The Terminal transmits each Batch that is ready to
send and a voice page, if there is one waiting.
3-6
