IBM 2790, Manual

Page: 17 / 88

Transaction
Nomenclature
Badge Reader
Operator Guidance
Lights
Manual Entry
Keyboard
Card Reader
Control Keys
Figure 9. IBM 2791 Area Station
The transmission line is divided into four segment. This
transmission-line segmentation (Figure 8) permits access to
area stations on other segments even though one or more
segments become inoperable.
The 2790 transmission line provides 13 time-multiplexed
channels of data, all operating concurrently. Eight of these
channels operate at an effective data rate of approximately
100 characters per second per channel; the other five oper­
ate at approximately 20 characters per second per channel.
The lower-speed channels are used to send data to IBM 1053
Printers. The higher-speed channels are used for all 2790
system input devices and for broadcasting time of day to the
2791 visual display.
Delete-Blanks Option
The delete-blanks option is a customer option that is wired
by the customer engineer when the area station is installed.
When the option is wired ON, blank columns from the AS
badge reader, 1035 Badge Reader, or Digital Device Read-In
feature are deleted from the data transmitted to the system
controller. When the option is wired OFF, the character
X‘40’ is sent to the system controller for each blank column.
Card Reader
The card reader is located on the right front (Figure 9) of
the area station and accepts alphameric and special charac­
ters (Figure 10), translating them to Extended Binary Coded
Decimal Interchange Code (EBCDIC) for transmission to
the system controller. Blank columns are not transmitted to
the system controller. End of card (EOC) is sensed by either
reading an EOC character or by sensing the end of the card.
Card-reading rate is approximately 60 characters per second.
Cards are inserted in the card receiver, face up, column-one
end first. An upper left corner cut is required to ensure that
the card has been entered properly.
Badge Reader
The badge reader in the area station is located in the upper
front of the station (Figure 9). The badge reader reads ten
columns of numeric information. Information from the
badge moves onto the communications network from high
order to low order (013 Badge Punch column 13 to
column 22). Blank columns in the badge are transmitted
to the system controller unless the delete-blanks option
is activated.
Area Stations 17