User's Manual

SALCOM 12-90 PAGING TRANSCEIVER AND STORE FORWARD REPEATER Issue 1290UB 0211
Sea Air and Land Communications Ltd Page 15
STORE FORWARD REPEATER OPERATION
When the store forward repeater option has been enabled the 12-90 will immediately
queue messages that have been received for transmission again when possible.
When used as a store forward repeater each store forward repeater should have a
unique unit ID. Changing the unit ID results in a varied pre transmission delay that
prevents multiple store forward units from all transmitting at the same time. Although
the 12-90 checks the channel if busy before transmission, if the unit ID is the same all
units believe that the channel is clear at exactly the same time which may result in
message collisions.
A duplicate message check is performed when in this mode that prevents any same
message that has been received in the last 40 seconds from being retransmitted. This
prevents the possibility of messages bouncing back and forwards between units. The
duplicate message reject functionality is also applied to messages received via the
serial port.
Transmissions are timed when configured as a store forward repeater. A lock out
period equal to the last transmission time prevents any further transmission attempts
until the next store forward in the chain has had time to clear the next message
(together with channel busy checking).
Store forward units must all be configured to be the same baud rate and message type.
UNIT NUMBER
Each unit will respond only to messages containing a matching unit ID or a group ID of
00. Up to 99 unique unit numbers are available when configured as a numeric receiver
(00-99). Approximately 8000 unique unit codes are available when used as an
alphanumeric receiver (any 2 printable characters). Any number of units can be
programmed with the same unit number.
RADIO CHANNEL FREQUENCY
The frequency of the radio channel can be preset at the SALCOM factory as required,
or can be modified by the user without the need of test equipment. The nominal receive
range is 440 to 479 MHz. The receiver bandwidth is narrow ensuring high sensitivity
and is suitable for 12.5kHz channel applications.
CONFIGURATION
All serial commands are sent and received using a standard terminal application
connected at 9600:N:8:1 using a 12-45 programming adaptor.
SALCOM 12-90 PAGING TRANSCEIVER AND STORE FORWARD REPEATER Issue 1290UB 0211
Sea Air and Land Communications Ltd Page 16
Sending MAP<CR> to the 12-90 will display current configuration information.