In early 1980s computers became popular not only as 
		work tools or scientific machines, but as toys to play games. Consoles 
		with built-in or cartridge games were around since late 70s. The idea of 
		"home computer" - computer with keyboard and programming language, but 
		also capable of displaying graphics and animation needed for games, 
		started to be implemented in many computers.
		Mattel Electronics, a video game division of Mattel toy company, got its 
		most success from video consoles like Intellivision. It was designed by 
		British company Radofin and manufactured in Hong Kong. When Mattel 
		decided to step into home computers business, a simple way of getting a 
		computer was getting it from Radofin.
		In early 1980s, Radofin already had 2 designs of microcomputers. Simple 
		one, internally codenamed "Checkers" and advanced model (codename 
		"Chess"). The first has been released in 1983 as Aquarius and the plan 
		was to release the second as Aquarius II. 
		The first Aquarius machines were sold below manufacturing price. The 
		gain was in its peripherals and cartridges, which had games, memory 
		expansions, ports, joypads or 300-baud modem. Even a CP/M emulator 
		cartridge has been announced. Unfortunately, 4kB of RAM was too small 
		for any serious work except learning BASIC, which occupied most of RAM 
		already. The BASIC was also limited (however only very first units have 
		BASIC without FOR instruction) and peripherals releases became more and 
		more delayed. Maybe because they ordered porting CP/M to the company 
		which designed power supply units? Graphics was not programmable easily. 
		Finally Mattel passed all computer busines to Radofin 4 months after 
		releasing Aquarius. Radofin made it for few years trying to sell it here 
		and there under different brands, but never made a big success.
		Right before ending microcomputer business, a small number of Aquarius 
		II computers have been released (by Radofin), but it was not machine 
		previously known as "Chess". It was an extended Aquarius I. The only 
		differences were casing, full-stroke keyboard and extended BASIC in 
		ROM... still using 4kB of on-board RAM made a 20kB RAM cartridge a 
		must-have. The "Aquarius III", real "Chess" machine has never been 
		released.
		This is the first Aquarius model released shortly after Mattel passed it 
		to Radofin, probably for German market. It has a Z80 running at 3.5MHz, 
		4kB of RAM and built-in TV modulator. Its small keyboard is not very 
		comfortable but usable, and graphics capabilities are, for that time, 
		below average (80x72 in 16 colors). Although most games were released on 
		cartridges, it has tape recorder connector.
| Manufacturer | Radofin / Mattel | |
| Origin | UK | |
| Year of unit | 1983 | |
| Year of introduction | 1983 | |
| End of production | 1987? | |
| CPU | Z80 | |
| Speed | 3.5MHz | |
| RAM | 4kB (cartridge expansion possible)  | 
			|
| ROM | 8kB | |
| Colors: | 16 | |
| Sound: | 1-voice | |
| OS: | BASIC,  machine-code games on cartridges  | 
			|
| Display modes: | 80x72 16colors graphics 320x192 graphics 24x40 Text mode  | 
			|
| Media: | Cartridges, tape | |
| 
				 Power supply: External on permanently fixed cable. UNREGULATED: Small warning: Original power supply's transformer is quite "soft" and has even +/- 24V when not loaded.  | 
			||
| I/O: | System bus / Cartridge 
				connector RF output Tape I/O Serial printer  | 
			|
| Possible upgrades: | Possible by cartridge expanders | |
|   Accessories in collection:  | 
			||
| Software accessibility: | Fair (TOSEC) | 
My unit is in a good condition, it was sold for German market as it has German manuals, yet in its box there are markings in French and English too. Probably it's Mattel unit re-branded back to Radofin, as most components are from 1983 and there is still "MATTEL ELECTRONICS" visible in plastic on the bottom and under the cartridge connector cover.
Important notes about hardware:
 - Most I/O ports are connected right to chips pins WITHOUT ANY PROTECTION. 
		Pay attention to peripherals. 
 - Power supply unit is only a transformer, rectifier and set of 
		capacitors. Output voltage without any load is usually +/-24V on 12V 
		lines and +12V on 5V line. This voltage is regulated inside computer.
 - Power pinout on mainboard:
		____               
		_______
		   | /\ /      
		\
		RF | \/ \______/
   |     ____
   | O   1234
 __|_______________ <-mainboard edge
		
		1 - +12V 150mA (unregulated)
		2 - GND 
		3 - +5V 1,2A (unregulated)
		4 - -12V 10mA (unregulated)
| Contents: | Starting | Recording media | Pinouts | Links | 
The machine starts and offers option to boot to BASIC by displaying "BASIC Press RETURN key to start" on slowly blinking screen. If you press Return then, it'll start MS BASIC from 1982.
To save your current program on tape, use CSAVE (CTRL-A) and program name in quotes:
CSAVE "MYPROG"
Program names can be 6 characters max. Then you press 
		Record on tape deck and Return on Aquarius.
		Verifying saved program is with CLOAD? command.
		
		To load program, use CLOAD (CTRL-Z) followed by program name in quotes:
CLOAD "MYPROG"
or just empty CLOAD to load first program it encounters. It should respond like "FOUND "MYPROG"" and load. If you type the program name and other program will be encountered on tape, its name will be shown and loading it will be skipped.
Generally there are two formats: BIN, which are direct 
		binary dumps of ROMs used in cartridges and CAQ, cassette dump format. 
		CAQ can be used in emulator like
		Virtual Aquarius or 
		converted to WAV by CAQ2WAV tool available in Virtual Aquarius package.
		Another emulator is AqEmu, also made in early 2000s.
		Tape:
| 
					 
					  | 
				
| 1 - Output (to recorder) 2 - GND 3 - Input (from recorder)  | 
				
Serial printer:
| 
					 
					  | 
				
| 1 - GND 2 - DSR? 3 - TxD  | 
				
1200baud, 8-bit, no parity, 1 stop bit, hardware handshaking 
			(DTR/DSR). 
			RS232-levels compatible, not TTL. Yes, you can
			LPRINT 
			to a PC terminal.
		http://www.reocities.com/emucompboy/ - Virtual Aquarius emulator, 
		along with CAQ games and tool (CAQ2WAV) to play them back.
		
		https://archive.org/details/Mattel_Aquarious_TOSEC_2012_04_23 - 
		Mattel Aquarius TOSEC software supplied by Archive.org. Mostly binary 
		cartridge dumps, some CAQs.
		
		http://www.digitpress.com/faq/aquarius.htm - Mattel Aquarius FAQ.
		
		
		http://www.vdsteenoven.com/aquarius/ - In collection.
		
		http://www.vdsteenoven.com/aquarius/techinfo.html - Very good 
		technical page.
		
		http://oldcomputers.net/aquarius.html - Another collector's 
		description.
		
		http://computermuseum.50megs.com/brands/aquarius.htm - Nice history 
		description
		
		http://www.notanon.com/tag/mattel-aquarius/ - Composite video output 
		by use of MAX4090 chip
		
		http://bhabbott.net.nz/micro_expander.html - Aquarius modern 
		expander.