User's Manual

SALCOM 12-90 PAGING TRANSCEIVER AND STORE FORWARD REPEATER Issue 1290UB 0211
Sea Air and Land Communications Ltd Page 11
If the unit ID, message length and checksum match that of the transmitted message, then
the message has been received, and does not need to be re-transmitted. (See “Virtual
Outputs and Control” for more information.
SALCOM 12-90 PAGING TRANSCEIVER AND STORE FORWARD REPEATER Issue 1290UB 0211
Sea Air and Land Communications Ltd Page 12
SERIAL PASSTHROUGH
The 12-90 can be used to pass raw serial between 12-90 units to form a simplex back to
back serial link using a 12-45 serial lead. The serial can be passed to many destinations
at once. This mode is well suited as a cost effective link between Salcom 12-76 telemetry
units.
The serial mode must be first configured to be ‘2'. Since the cap code and paging
information is not supplied this is taken from the first cap code specified in the first cap code
range. The performance of the serial link can be improved considerably by using a cap
code that is divisible by 8 - such as 1234560. This cap code must match both the source
and destination units. The RX mode must be set to A1200 (auto set when option is
enabled). In this mode if configuration changes need to me made the first character after
cycling the power must be the ‘+’ character, preventing accidental configuration changes
by random commands.
Connection speed at source and destination is 9600:N:8:1 but internally the speed is set
to the paging transmission speed (1200 baud by default). Some message buffering is
possible (100 characters) but continued transmission at 9600 will result in data loss. The
message “BUSY” will be returned from the 12-90 when there has been a buffer overrun.
Serial data is transmitted immediately (if the channel is clear) after a carriage return, or
after 100 mS of serial inactivity. Only ASCII characters between 0x01 and 0x7f can be
transmitted.
Benefits:
• Serial broadcast to many units simultaneously is possible.
• Serial data is packetized and contains bit error correction information which may
outperform traditional radio modems in noisy environments.
SERIAL MESSAGES
The following messages may be seen during normal operation.
Startup Message: SALCOM 12-90 V1.21<CR>
Error Messages:
BUSY<CR> Transmission queue is full. Try again later.
Q FULL<CR> When configured as a store forward unit the received
message was dropped because there was no message
queue space available.
Info Messages:
CHAN BUSY NN<CR> Waiting to transmit - there is someone already transmitting on
the channel - The 12-90 will transmit when able to. NN
provides information as to how busy the channel was.
DUPL<CR> When configured as a store forward repeater this message