The '46A, '47A, and 'LS47 feature active-low outputs designed for driving,
common-anode LEDs or incandescent indicators directly. The '48, 'LS48, and
'LS49 feature active-high outputs for driving lamp buffers or common-cathode
LEDs. All of the circuits except 'LS49 have full ripple-blanking input/output
controls and a lamp test input. The 'LS49 circuit incorporates a direct blanking
input. Segment identification and resultant displays are shown below. Display
patterns for BCD input counts above 9 are unique symbols to authenticate input
conditions.
The '46A, '47A, '48, 'LS47, and 'LS48 circuits incorporate automatic leading
and/or trailing-edge zero-blanking control (RBI\ and RBO\).
Lamp test (LT\) of these types may be performed at any time when
the BI\/RBO\ node is at a high level. All types (including
the '49 and 'LS49) contain an overriding blanking input (BI\), which
can be used to control the lamp intensity by pulsing or to inhibit the outputs.
Inputs and outputs are entirely compatible for use with TTL logic outputs.
The SN54246/SN74246 and '247 and the SN54LS247/SN74LS247 and 'LS248 compose
the 6 and the 9 with tails and were designed to offer the designer a choice between
two indicator fonts.
