GLB Electronics Inc SX150EN11C-G Manual Do Utilizador
GLB Electronics, Inc.
SNRDS Manual
1-2
GLB Synthesized Netlink Radio Data System
01/04/00
access accumulated information. If memory overflows, new data is not accepted from other stations until enough
information has been accepted by the host, releasing sufficient memory space.
information has been accepted by the host, releasing sufficient memory space.
Any SNRDS station may be used as a relay point, or “digipeater” to forward packets from other stations which may
be too distant for a direct radio link. Up to 8 digipeaters can be included in an address field to relay packets
through specified stations to the destination if the destination site can’t be reached directly. Watchdog hardware on
SNRDS ensures that the system runs reliably by resetting the CPU automatically in the event that CPU operation is
disrupted. SNRDS also may be remotely controlled via a radio connection.
be too distant for a direct radio link. Up to 8 digipeaters can be included in an address field to relay packets
through specified stations to the destination if the destination site can’t be reached directly. Watchdog hardware on
SNRDS ensures that the system runs reliably by resetting the CPU automatically in the event that CPU operation is
disrupted. SNRDS also may be remotely controlled via a radio connection.
A message can be stored, to be transmitted automatically to another station each time it connects, or it can be made
to transmit periodically to an independently entered address (beacon mode).
to transmit periodically to an independently entered address (beacon mode).
By providing access to the disk operating system (DOS) in the host software, files can be transferred to and from
disk and/or to another station’s disks directly. Appropriate host programming would allow such exchanges to take
place as background tasks, freeing up the host computer to continue other operations transparently to the operator.
Information could be directed to devices such as disk files, printers or other I/O ports.
disk and/or to another station’s disks directly. Appropriate host programming would allow such exchanges to take
place as background tasks, freeing up the host computer to continue other operations transparently to the operator.
Information could be directed to devices such as disk files, printers or other I/O ports.
Two protocols are supported, called MX.25 and LOP (Low Overhead Protocol). MX.25 has more features, but LOP
is simpler and more efficient in many applications. The protocol may be selected by command, but when called
from another station the protocol used by the caller is selected automatically.
is simpler and more efficient in many applications. The protocol may be selected by command, but when called
from another station the protocol used by the caller is selected automatically.
The software provides great flexibility, with commands that can be used by the host computer to implement
specialized protocols. Within the HDLC format, any kind of frame can be generated and sent by the host, and the
host can screen received frames and implement custom responses.
specialized protocols. Within the HDLC format, any kind of frame can be generated and sent by the host, and the
host can screen received frames and implement custom responses.
1.3. Hardware features
SNRDS is supplied in an RF-tight aluminum housing measuring 9.775 D by 2.27 H by 4.54 W inches (24.83 x
5.77 x 11.53 cm). All interconnects are on the rear panel and all indicator LED’s are on the front panel. This
arrangement leaves the remaining four surfaces unobstructed.
5.77 x 11.53 cm). All interconnects are on the rear panel and all indicator LED’s are on the front panel. This
arrangement leaves the remaining four surfaces unobstructed.
The on-board controller provides commands for setting the operating frequencies of the receiver and transmitter,
which have independent frequency synthesizers. There are no crystal ovens, so there is no warm-up delay. The
CPU is supported by 64K of memory, non-volatile memory backup and panel display. In the original RDC, a
lithium battery retains the contents of memory when power is removed from SNRDS. The RDC2 and up have non-
volatile memory for storing critical parameters.
which have independent frequency synthesizers. There are no crystal ovens, so there is no warm-up delay. The
CPU is supported by 64K of memory, non-volatile memory backup and panel display. In the original RDC, a
lithium battery retains the contents of memory when power is removed from SNRDS. The RDC2 and up have non-
volatile memory for storing critical parameters.
There are two hardware “watchdogs” to ensure reliable operation. A CPU watchdog resets the program if the
software should become disrupted. In addition, there’s a limit timer in the transmit keying circuit to limit the
length of any single transmission in case of complete controller failure.
software should become disrupted. In addition, there’s a limit timer in the transmit keying circuit to limit the
length of any single transmission in case of complete controller failure.
Primary communications with the terminal or computer are carried out via an RS-232 serial port. A secondary
serial port has limited functions at this time, but in future releases of software this second port will become a
separate, fully addressable port such that two RS-232 devices can be connected to one radio. To keep the panel and
installations simple, standard SNRDS bring out all connections except the antenna jack and power input via a
single DB-25S connector. A second RF connector is available for transceivers, providing independent antenna
connections to the receiver and transmitter.
serial port has limited functions at this time, but in future releases of software this second port will become a
separate, fully addressable port such that two RS-232 devices can be connected to one radio. To keep the panel and
installations simple, standard SNRDS bring out all connections except the antenna jack and power input via a
single DB-25S connector. A second RF connector is available for transceivers, providing independent antenna
connections to the receiver and transmitter.
Antenna switching is accomplished with PIN diodes for fast turnaround operation. In packet applications the path
should “turn around”, or go from receive to transmit and vice-versa, very frequently. Slow turnaround time reduces
the link data throughput and increases the probability of collisions. SNRDS radios turn around in 10 milliseconds.
A half-duplex version is also available, which requires no switching and has two RF panel BNC’s, one for the
transmitter and one for the receiver.
should “turn around”, or go from receive to transmit and vice-versa, very frequently. Slow turnaround time reduces
the link data throughput and increases the probability of collisions. SNRDS radios turn around in 10 milliseconds.
A half-duplex version is also available, which requires no switching and has two RF panel BNC’s, one for the
transmitter and one for the receiver.