TM 5-6675-318-14
The data entry and display board is also the interface between the printer and
processor.
It receives data from the printer in serial RS-232 format and converts
t h e d a t a t o 8 - b i t p a r a l l e l f o r t r a n s f e r t o t h e p r o c e s s o r . I t r e c e i v e s 8 - b i t
parallel data from the processor and converts the data to serial RS-232 data for
t r a n s f e r t o t h e p r i n t e r.
The communication interface to the printer is normally
configured at the factory for a 20-mA active current loop.
To convert the interface
to a 20-mA passive current loop, the printed circuit etch between E-points E9 and
E10 must be cut.
i .
Modem board (b) allows the satellite surveyor to communicate with another
satellite surveyor via an external communications link connected to the MODEM
INTERFACE I/O connector.
Signal format and message rate are serialized digital
data at 125 baud.
The board encodes and decodes the digital data, employing
phase modulation, and communicates with the Z80 microprocessor on the processor
board via a bidirectional data bus .
The board also incorporates a relay con-
tact output for keying a radio transmitter.
j .
Tape control board (c) is the interface between the processor and the tape
c a s s e t t e t r a n s p o r t.
Tape speed is regulated by the tape control board to read or
write data at 8000 bits per second.
Tape status bits are detected and passed to the
processor by this board.
The tape control board provides timing, buffering, and
s e r i a l - t o - p a r a l l e l , a n d p a r a l l e l - t o - s e r i a l c o n v e r s i o n s i n b o t h r e a d a n d w r i te
modes.
As data is written on and read back from the tape cassette, a redundancy
check is performed to provide a unique value for each tape record.
This value is
checked with the calculated value,
If the values do not compare, an error is
generated.
Power-on signals from the alarm clock board apply power to the tape
control board through two relays when in full power operation.
k. The 5 MHz reference oscillator provides a very stable reference frequency for
use throughout the receiver/processor.
An external 5 MHz may be connected to the
receiver/processor and can be selected for use by the INT/EXT oscillator switch
i n s i d e t h e s a t e l l i t e s u r v e y o r.
T h e a c c u r a c y o f t h e i n t e r n a l o s c i l l a t o r i s 8 x 10
- 12
over a 100 second interval.
l .
The power supply board has an input of 10.5 to 16 v dc from an external
source and generates all voltages necessary to operate the satellite surveyor
through two independent regulator circuits.
One regulator supplies power in the
reduced power mode to only the alarm clock board,
o s c i l l a t o r , a n d b a t t e r y c h a r g e r.
The second regulator is controlled by the alarm clock board and provides operating
v o l t a g e s t o a l l o t h e r c i r c u i t s w h i l e i n f u l l p o w e r o p e r a t i o n.
The battery charging
circuits fast charge and maintain a constant voltage on the internal batteries.
m. The internal batteries are rechargeable 12 V dc lead acid batteries. The
batteries supply power to the alarm clock board, oscillator,
and memory when the
external power supply is disconnected, the ON/OFF switch is in the ON position, and
the STANDBY/OPERATE switch is in the STANDBY position while the satellite surveyor
i s b e i n g t r a n s p o r t e d f r o m s i t e t o s i t e .
The internal batteries will supply power
for approximately 20 hours.
Change 2
4-13
