User's Manual

Operation
RFI-148 & RFI-900 High Output Power Paging Transmitters User Manual Page 27 of 134
• Software PTT: Software PTT is available using Hayes AT commands, through the Cruise Control
GUI, or through the terminal menu interface. It is also selected implicitly when enabling TNPP or
PET/TAP on either a serial or Ethernet stream.
• Hardware PTT: Hardware PTT is available through the LIU connector. Hardware PTT can be
configured to be active high or active low. The delay from hardware PTT to transmitter on and data
ready is 10 ms.
• Auto PTT: Auto PTT is performed by detecting a change in the data bits on the LIU and turning on
the transmitter. When using auto PTT some preamble will be lost; some encoders may need to increase
preamble time.
Hardware PTT can be enabled using the “Encoder Hardware PTT” option and auto PTT can be enabled using
the “Auto PTT” option in the “Encoder Interface” menu. Hardware PTT and auto PTT cannot both be enabled
at the same time.
PTT TURN OFF DELAY
The unit has the option to leave the transmitter on for a set duration after receiving a PTT off signal. This delay
is driven by software and typically accurate to 100 ms.
TRANSMIT TIMEOUT
The unit can automatically raise a fault if the transmitter has been transmitting for too long. By default, the
transmit timeout feature is disabled. If enabled, the transmit timeout fault causes the transmitter to key down
and set the PTT system override to disable transmit. See section 5.2.1 for more information on fault actions.
PTT OVERRIDE
Transmitter PTT can be completely disabled which stops the paging transmitter from transmitting. PTT
override can be changed using the “PTT override” setting.
In some cases the paging transmitter will disable itself from transmitting. If PTT override is disabling transmit
the “PTT Override Status” will describe what caused the override. There are five circumstances where the
paging transmitter will override PTT:
• User: The PTT override has been configured to “Disable Transmit”.
• Listening: The isolator mode is set for listening (for operation of the isolator see section 4.3.6).
• Fault: The disable transmit fault action is active (for more on fault actions see section 5.2.1).
• Loading Config: Cruise Control is loading a configuration file.
• In Standby: The unit is in Standby due to the Hot Standby operation (see section 7).
PTT is enabled once the source of the override is addressed.
Radio -> PTT Turn Off Delay
Radio -> Transmit Timeout
Radio -> PTT Override