Plantronics Colorplus

The Plantronics Colorplus is a graphics card for IBM PC computers, first sold in 1982. It implements a superset of the then-current CGA standard, using the same monitor standard and providing the same pixel resolutions. It was produced by Frederick Electronics, a subsidiary of Plantronics since 1968, and sold by Plantronics' Enhanced Graphics Products division.
The Colorplus has twice the memory of a standard CGA board. The additional memory can be used in graphics modes to double the color depth, giving two additional graphics modes—16 colors at resolution, or 4 colors at resolution.
It uses the same Motorola MC6845 display controller as the previous MDA and CGA adapters.
The original card also includes a parallel printer port.

Output capabilities

CGA compatible modes:

16 color mode
in 4 colors from a 16 color hardware palette. Pixel aspect ratio of 1:1.2.
in 2 colors. Pixel aspect ratio of 1:2.4
with pixel font text mode
with pixel font text mode

In addition to the CGA modes, it offers:

with 16 colors
with 4 colors
"New high-resolution" text font, selectable by hardware jumper

The "new" font was actually the unused "thin" font already present in the IBM CGA ROMs, with 1-pixel wide vertical strokes. This offered greater clarity on RGB monitors, versus the default "thick" / 2-pixel font more suitable for output to composite monitors and over RF to televisions but, contrary to Plantronics' advertising claims, was drawn at the same pixel resolution.

Software support

Few software made use of the enhanced Plantronics modes, for which there was no BIOS support.
A 1984 advertisement listed the following software as compatible:

Color-It
UCSD P-system
Peachtree Graphics Language
Business Graphics System
Graph Power
The Draftsman
Videogram
Stock View
GSX
CompuShow

Some contemporary software has added support for Plantronics modes: Planet X3, released by American YouTuber David "The 8-Bit Guy" Murray in 2019, was the first video game known to have Colorplus support. This support was added by Planet X3 enthusiast Benedikt Freisen.Attack of the Petscii Robots by American YouTuber David "The 8-Bit Guy" in 2020, ported to MS-DOS computers with a graphics mode providing support for Plantronics Plus.

Benedikt Freisen produced updated drivers in 2021 that add Colorplus support to Sierra's adventure games that ran on Sierra's Creative Interpreter.FastDoom, a port of Doom (1993 video game) developed by Victor Nieto, added support for ColorPlus with 16 colors mode in 2021.

Hardware clones

Some third-party CGA and EGA clones, such as the ATI Graphics Solution and the Paradise AutoSwitch EGA 480, could emulate the extra modes.
The Thomson TO16 and the Olivetti M19 supported Plantronics modes, along with CGA.