'Italic text'Italic text'=== Open Circuits ===
These should be projects or links to projects that are open, at a minimum in the sense that there is enough information so that others can reproduce the project. Lets stay away from sites that are just show cases without the details.
- 1 Programmable Chip EEG
- 2 Open Source Disability Gadgets
- 3 µWatch
- 4 Open Source Circuits Magazine
- 5 Open OBDII
- 6 vehicles: manned and unmanned
- 7 Phone line relay controller with PIC16F84A - single relay
- 8 Phone line relay controller with PIC16F876A - 6 relays!
- 9 Homemade MIDI turntable
- 10 Motherboards that Run Linux
- 11 Open Mobile Gadgets -- open source, open hardware, mobile phone
- 12 Music Players including MP3 players
- 13 PG31 GPS RS232 Dev Board
- 14 PG31 GPS USB Dev Board
- 15 RS232 Dev Board
- 16 RS232 RS485 USB Converter Board
- 17 Number Six
- 18 LED and POV displays
- 19 Cellular Rotary Phone
- 20 Das Brewmeister! and Fermenter Controller
- 21 Home controller
- 22 Interactive Lock Box
- 23 Motor driver (H-bridge)
- 24 atomic microscope
- 25 BlueICE
- 26 Sort-of-Networked RFID Reader
- 27 Battery charger
- 28 the Open Graphics Project
- 29 Amiga floppy project
- 30 Irsensor-a
- 31 DsPIC30F 5011 Development Board
- 32 Ethernet Module
- 33 Modulation Plugin
- 34 Scavenge
- 35 Wiegand reader simple controller
- 36 ComClone2 Intercom
- 37 Minimig
- 38 USB Audio Streamer : A Homebrew USB Soundcard
- 39 PINGPONG-CDC : A Homebrew USB FHSS RF Modem
- 40 XE1205-RNDIS : FCC Legal Frequency Hopping Spread Spectrum USB Wireless Ethernet
- 41 An acceptable third generation PostScript printer
- 42 the Kestrel
- 43 astronomy
- 44 flash downloaders
- 45 WikiNode
- 46 arm7-oled-clock
- 47 Sun SPOTs
- 48 GPIB
- 49 Other Lists of Semi-Open Projects
- 50 other project sites or links to projects
The Programmable Chip EEG is a Multi-channel electroencephalograph that could be a brain-computer interface. See the OpenEEG Project
Open Source Disability Gadgets
- "Gear and software for people with disabilities is usually ... hard or impossible to repair it, or get anyone to repair it. We need to hack the model for accessibility tools! With a culture of open source designs, Instructables, wikis, and blogs" -- Open Source Disability Gadgets: DIY for PWD
- µWatch: World's First D-I-Y Scientific Calculator Watch
Open Source Circuits Magazine
Anykits magazine - Anykits publishes an open source magazine with quite a few, application oriented circuits. It contains schematics, parts list and PCB illustrations. The best part is that its formated for print and available as regular PDF.
Link to source and schematics Open source hardware and software implementing OBDII tester for cars. Two versions one using a PIC microcontroller and one using an AVR microcontroller.
vehicles: manned and unmanned
Lots of vehicle-related projects -- for motorcycles, automobiles, and unmanned aerial vehicles (UAVs).
Phone line relay controller with PIC16F84A - single relay
-  controll one relay over phone-line. Uses PIC16F84A and MT8870.
Phone line relay controller with PIC16F876A - 6 relays!
-  controll up to 6 relays over phone-line. Uses PIC16F876A and MT8870.
Homemade MIDI turntable
Cheap and simple homemade MIDI turntable with GPL2 license. Using a ATmega, a HDNS-2000 optical mouse encoder, GCC-AVR, AVR-Libc and FreeRTOS. Homepage of Homemade MIDI turntable.
Motherboards that Run Linux
An ARM920T board running Linux at 200 Mips with sound, Ethernet, CAN, 48+ bidirectionnal IOs and 4 DSPs for motor control (DC, Servos, etc...). Built as a student proof robotics design platform.
The Balloon project has produced Balloon3, a high-performance ARM board designed for use by OEMs and Higher education. Spec is PXA270 (583Mhz), FPGA or CPLD, 1GB flash, 784MB RAM, USB (master, slave, OTG), CF slot, expansion bus, 16-bit bus, I2C, LCD, serial, audio. Very low power in CPLD confiuguration. Small, light. Various add-on boards: VGA LCD driver, robot motor driver+A/D, digital IO. Released under the Balloon Open Hardware license, which allows anyone to manufacture and for people to make derivatives. The expansion bus allows balloon to be used as the computing component for various special-purpose devices.
The linuxstamp is an open source processor module. It is designed to be a very simple board capable of running linux. It is based on the Atmel AT91RM9200 processor (An ARM9 processor with a MMU).
This is the first mother board for the linuxstamp. It is still in the planning stages (no pcbs).
"All CAD files required for building LART are available under the closest we could get to an Open/Free Hardware License." (Has this information gone offline?)
Other Boards that Run Linux
- Is it possible to Linux on a "soft CPU" inside a FPGA?
Open Mobile Gadgets -- open source, open hardware, mobile phone
An open source, open hardware mobile phone in its preliminary development.
Music Players including MP3 players
- TRAXMOD Open source MOD music player for dsPIC/ARM microcontrollers.
- Music Player Mostly off site.
A simple RS232 example project that takes 3.3V TTL serial and outputs to a super-common RS232 connection. Insto-NMEA!
A great example project using the CP2102 USB to TTL UART IC as well as some basic battery holder info.
A simple RS232 example project that takes all the power it needs from the serial port. Use it to power your microcontroller and communicate between serial port and microcontroller. Takes advantage of the fact that pc serial ports will accept 0-5V rather than the RS232 standard of around negative 10V to positive 10V. Very convenient - no external power required! Note that you may use either a 5.1V Zener or a 5V regulator.
Aim to build a general Converter between different Interfaces.
"#6" (the son of Chalk Roach) is a ultra simple microcontroller development board for Atmel ATmega32 = 16MHz, 2KB SRAM, 16KB Flash
LED and POV displays
Led displays range from a battery and an LED which light up ( cool!, add a magnet and you have an led throwie ) to microcontroller led projects, either Smart Led ( Led with a microcontroller so that it blinks, reacts to the environment, or shifts color ) or Led Arrays ( or led matrix ) that do simple graphics and or play games, or POV devices where what you see depends upon you persistance of vision ( which can include some led arrays ). You can probably dig up more using these terms in google.
Our Own Projects
- 24" Wall Clock A really big wall clock. Why? Well, cause it might look cool? Probably not. But we do use GPS to get the time! Groovy.
- POV display that spins around, giving the illusion of a large display. (DavidCary)
- PointLess LED Array A 8 by 8 array displays something using POV (russ_hensel)
- PIC Links and search on POV and/or LED
- Bicycle LED POV is an electronic LED bar to attach on bicycle wheels. When riding the bicycle, the LED bar will draw with light, text messages and image animations. Free/Open hardware, firmware and software.
- "luscious electric delight": source and schematics for a large graphical LED panel. Uses 12 MAX6953 LED drivers; each MAX6953 drives four 5x7 led matrices. The PC generates arbitrary bitmap, sends it out the serial port to a PIC, which translates it to I2C bus connected to all the MAX6953 LED drivers, which update the image at a continuous frame rate of 30fps.
- BlinkenProjects: projects with lots of LEDs, including a 3D LED array. Wiki: http://wiki.blinkenarea.org/
- Ian’s Spoke POV Review it.
- Project: Super POV Review it.
- SpokePOV Persistence of Vision for your Bike Very nice, kit available.
- On this page you will find a scrolling LED sign based on the ATtiny2313 AVR microcontroller Row Column approach with a shift register]
- Flashing LED Bra
- "Peggy," A Light Emitting Pegboard Display
- Christmass trees are now led based so: The #1 Site for Controlling Christmas Lights with a Computer
- Don Klipstein's LED Main Page Lots of good info.
- Synchronizing Fireflies ATtiny super smart swarm of LEDs.
- U-Disp - An Open Sourced USB display
- Sunrise LED Alarm Clock ATMega8515 controlling two color-mixed high-power LED channels with PWM. Also contains a RTC circuit and a serial port. Full source including PC Windows serial port communication code.
An indepth breakdown of the Port-O-Rotary. Some clues to help you avoid audio problems with the GM862.
- Das Brewmeister! : An attempt to wirelessly monitor temperatures of fermentation vessels
- Fermenter Controller : A web available fermenter vessel controller. Uses PICs, I2C, Rs232 and python.
Program your appliances to operate automatically in conjunction with your weekly and daily schedule, manually turn them on/off from your PC or use the controller as a process ON/OFF controller to regulate some kind of physical variable to the desired value.
An interesting project using an accelerometer and capacitive touch ICs.
Motor driver (H-bridge)
An atomic-resolution microscope.
- STM (scanning tunnelling microscope)
- AFM (atomic force microscope)
A bluetooth JTAG ICE debugger for AVR's!!!
Sort-of-Networked RFID Reader
A 125Khz RFID Reader with a simple ring network - to allow connection of multiple units to the same control computer.
See "Build A Smart Battery Charger Using A Single-Transistor Circuit" by Ejaz ur Rehman. But be sure to read the "Reader Comments" at the end. The suggestion to add a zener diode is a good idea.
the Open Graphics Project
the Open Graphics Project a project started by chip-designer Timothy Miller. His goal, along with the rest of the project, known as the “Open Graphics Foundation” is to make a 3D accelerated video card which is fully documented, free-licensed, and open source. See the Open Graphics wiki.
The Amiga floppy project: designing, building, and programming an adapter to allow PCs to read from Amiga floppies. "This is really designed to be a community project(hence the blog with progress reports)."
This project is the building of an external USB amiga floppy drive controller. It sits between the USB port on a Windows PC, and a regular PC floppy drive. It will allow the PC to create .ADF images from an amiga floppy disk. This device is based on a Parallax SX28 microcontroller, uses Ramtron FRAM memory for temporary track storage, and uses another Parallax component for the USB interface.
See http://www.techtravels.org/amiga/amigablog for the latest in the blow by blow attempts to get this thing off the ground!!
Infrared Proximity Sensor Alfa Infrared Proximity Sensor Alfa in www.kedo.com.mx
The Infrared Proximity Sensor Alfa is a sensor to detect objects that can reflect infrared light. It has the following characteristics.
- Designed to detect objects that are close and can reflect infrared lights.
- It has a Infrared Transmitter to eliminate the dependency of solar lighting. So It can be used in the night.
- It has a Infrared Receiver that detects the closest object that reflects the infrared lights.
- It has an incorporated voltage regulator
- The output is a constant 5V when it is active and 0V when no detection.
- You can change the proximity threshold with a potentiometer.
A development board using Microchip dsPIC30F5011, a 5V based 16-bit microcontroller with DSP functions, EEPROM, ADC, PWM and communciation ports of UARTs, I2C, SPI etc. Contains concise information on:
- Development environments (IDE)
- External programming methods (ICSP Programming using ICD2 Programmer)
- Bootloader implementation (RTSP)
- Software development tips based on POSIX concepts
- Basic conversion tips to target board using Microchip dsPIC33FJ128GP306, a pin-to-pin compatible 3.3V microcontroller
- This project aims to develop an Ethernet Module, to be used in conjunction with a 8/16 bits embedded system such as the dsPic33F development board.
- The entire Ethernet Module consists of:
- Hardware: a LAN card based on Davicom DM9000A chip
- Software: a TCP/IP stack based on uIP 1.0 or lwIP
- This project aims to develop an Modulation Plugin Module, to be used in conjunction with a 8/16 bits embedded system such as the dsPic33F development board.
Some people derive an inordinate amount of pleasure from building semi-useful objects from zero-cost junk.
In the electronics field, most of the stuff built from scavenged components falls into 2 categories:
- ham radio transmitters and receivers -- built from a few transistors, caps, resistors, and wire
- BEAM robotics -- built from the above plus motors, solar cells, ...
According to http://coprolite.com/art12.html , "I'd love to hear about where you found your 8048. Take a picture of the host that you remove it from (CD player, truck, refridgerator, whatever) and I'll put your picture on a page that chronicles our adventures sifting through the rubble."
Also see Free_From_Salvage
RepRap is an open source project to create a 3d printer or fabber machine. There is tons of information available on its website. The current iteration is a 3 axis cartesian robot with 2 extruder heads: a Thermoplastic head that extrudes plastics like HDPE, ABS, and CAPA, and a support material head that extrudes a water soluble material to support the build process.
The Biollante project is a kind of RepRap that uses a 6 axis Stewart platform. Can devices from a mechanical model library be fabbed with RapRap? The article "Self-reproducing machines" goes even further than just 6 identical parts -- it suggests that "self-reproducing machines composed of many identical microscale modules" may be a better design than the original RepRap design where just about every part is unique.
"This is the meta-problem of engineering: Design a machine that can design other machines." -- Hod Lipson
Challenge: Build a Wiki Device with a parts cost of no more than twenty dollars which is usable as a portable wiki. Include feature to make it compatible with a desktop or laptop computer's PersonalWiki, with a connector allowing this use. -- http://c2.com/cgi/wiki?TwentyDollarWikiDevice
"hardware portable wiki for taking notes with an auto-merging functionality when you are very close to Internet or your computer." -- http://communitywiki.org/AlexandreDulaunoy
These are three boards that I designed for a specific project and found them very useful. Each of these boards uses the phoenix contact plugable terminal blocks. The 50-pin breakout board is for a 50-pin ribbon cable. The LEM breakout board is for LEM AC/DC current sensor. The power supply breakout board is for a +5v +/-15v power supply.
Free Telephony Project
- Embedded Asterisk IP-PBX hardware and software
- Low cost, completely open IP-PBX hardware including FXS/FXO analog and E1/T1 interfaces, and DSP motherboard hardware. Target price of $100 for a 4 port IP-PBX.
Eyes for Open Robot
- $20 CMOS Camera Module - 640x480 has a "Get-that-camera-working competition" discussion forum and now been adequately documented ... http://elinux.org/wiki/SparkfunCamera ... by David Carne.
- ... perhaps simpler to use an off-the-shelf webcam that plugs directly into a laptop ... Enabling Support for Your (Webcam) Hardware in Linux ... Philips USB Webcam Driver for Linux ... QuickCam ...
Is there a simple way for my Java application to fetch the latest camera image in an Array of pixel values?
- open architecture humanoid robotics platform --OpenHRP
RCAP: R/C Auto Pilot: Remote Control Auto Pilot
"The RCAP2 is a Remote Control AutoPilot] for model airplanes, cars and boats. The autopilot function can be switched off or on during flight with the flick of a switch." Uses PIC16F876A to:
- read (servo) commands from the RC server
- read (RS-232) GPS location from a NMEA capable GPS (with programmable goto/waypoints functions)
- drive (servo) commands to the rudder.
The PICmicro 16F628 decodes Wiegand protocol coming from card reader. If the card matches one of the 40 cards in EEPROM, it turns on the light (opens the door). Schematic and source code published under GNU terms.
ComClone2 is a DIY clone of the industry-standard "party line" production intercom system as first introduced by Clearcom and now sourced by many other vendors. This intercom system is widely used in both live show(theatrical, music, etc.) and video production. Website provides complete construction information including PC board, etc.
Amiga 500 implemented with Xilinx FPGA + Freescale mc68000
This project is a homebrew 12bit 24KHz homebrew USB soundcard based on a pic 18f2550 and a few Microchip analog parts. The project is based on the Microchip USB framework, but the core audio processing is written from scratch. The card is a duel Audio 1.0 + generic interface composite device with the generic interface being handled by WinUSB. The schematic, card firmware, and host C++ software is provided.
POV scrolling display with an RF connection to a mini-itx computer and weatherstation. Project is built out of 384 discrete red LEDs. Display shows time and date, sunrise/sunset time and outdoor/indoor weather.
Schematics, Board Layouts, and MPLAB C18 firmware source code is provided.
The PINGPONG-CDC project is a homebrew USB frequency hopping spread spectrum RF modem (FHSS). The modem is based on the Microchip 18F2550 and the Semtec XE1205 RF module. The module does not include a MAC or protocol layer. That is what this project implements. The project demonstrates how to write a FHSS MAC layer and use USB to interface it with a PC through CDC and WinUSB. Since the protocol is not hard-wired, it is easy to change the software to experiment with different protocols. A utility for pairing and configuring modems is included. The schematic, firmware, and host C++ software is provided.
This is the PINGPONG-CDC project that emulated ethernet through the RNDIS driver in Windows rather then a serial cable replacement. Full source code is provided.
An acceptable third generation PostScript printer
"Ask the Guru: A Third-Generation Printer" article by Don Lancaster 1990 http://www.tinaja.com/glib/guru60.pdf lists specifications for "An acceptable third generation PostScript printer." Would this be a good "open hardware" project ?
"About the Kestrel" by Samuel A. Falvo II 2004
The Kestrel's intended purpose is to be a rational, grass-roots computer design employing half-way modern technology, where (quite unlike the PC) *EVERYTHING* is documented openly. BUT, not adopting every possible technology under the sun just because it exists. ... you'd get the circuit schematics, register-level programming information, timing diagrams, and descriptions of the ROM-resident OS interfaces ...
The over-arching goals of the project remain the same:
- An open, completely documented architecture, able to be described in a SINGLE BOOK. ...
- Fan-less design, which means, low power, even at the expense of computation speed. ... I'm not aiming for the lowEST power -- but fanless design is critical.
- Instant on, (nearly) instant off. ... On the Amiga, you just waited 5 seconds, without touching anything, (that's it) for the disk caches to sync with the volumes, and then you flicked the power switch. End of discussion. Not so with Windows or Linux. Anyway, boot-up is way, way more expensive. It has to check RAM every freaking time ..., it probes the buses and takes its damn sweet time doing it, etc. AmigaOS did all this in a fraction of a second. Heck, even just spending 5 seconds is sufficient for me. But remember that this is added on to the start-up time of the OS you're loading too! The goal: instant on, instant off. Trust me -- it really DOES make a difference!
- Lightning fast I/O auto-detection. If the Amiga can do it with 8MHz processor technology, so can we with 66MHz. I simply cannot emphasize this enough.
- Relatively easy to build. Since this is now an advanced kit idea, this isn't nearly as weighted as it used to be. Nonetheless, it is a goal to strive for.
- Minimum cost. ...
The whole purpose is to have FUN with this computer -- to have fun building it, to have fun using it, to have fun expanding it. Part of this fun factor is being able to hack the hardware as much as you can hack the software. Commodore's IEC bus, HP's HP-IL, and Amiga's Zorro bus are all inspirations here. ... it wasn't hard to build a Zorro card that fully interoperated with the system, you didn't need to be registered with anyone but Commodore (and they gave away mfr IDs for FREE), and full hardware interface details were available in the Amiga HRM for a cost of $29.99 US. It was bliss.
- Everything is LGPLed. So if you DID want to include PCI slots or whatever, please feel free!! Just because it's not my personal priority with the system doesn't mean it's not someone else's. This is the beauty of open source and, indeed, open hardware.
- Support for new business opportunities. ... This ties into the prime goal of this whole thing, which is,
- The creation of a vibrant and healthy user and developer community, capable of supporting itself on both software AND hardware fronts.
A more up-to-date description of The Kestrel Project. (several other pages on the Kestrel project nearby).
A variety of "open" tools for optical and radio astronomy.
The WikiNode project tries to link every wiki in the world together. Our "WikiNode" links to closely-related wiki (and their WikiNode links back).
If you want to talk about something that is not quite on-topic here at Open Circuits (say, "desktop PC case modding", or "embedded Linux programming"), our WikiNode helps you find another wiki where people love to talk about that exact topic. The corresponding WikiNode on each of those wiki helps people who want to talk about "open hardware" to discover this wiki.
arm7-oled-clock is a clock hardware/software project for a clock with a graphic organic led display running on an atmel arm7 microcontroller.
Here is the arm7-oled-clock's project page on google code.
This Java-based system is an ARM920T 180MHz processor, 4Mbyte Flash, 512Kbyte pSRAM and 802.15.4 radio transceiver (TI CC2420). See the Sun SPOT World website for more information. We also have an active forum.
The hardware designs can be downloaded from https://spots-hardware.dev.java.net. The content available for download (subversion) are the schematics (pdf, Altium), bill of materials (Excel), assembly drawings (pdf), fabrication drawings (pdf), PC design files (Altium) and gerber files (RS274X) for these boards.
The boards we have posted are:
- eDemo: Demonstration add-on board for the Sun SPOT.
- eFlash: MiniSD card reader/writer add on board for Sun SPOT
- eProto: Prototype board with simple interface to Sun SPOT
- eProtomega: eSPOT Prototyping board with Atmega88 processor
- eSerial: RS232 Serial interface board for the Sun SPOT
- eUSB-Host: USB host interface to Sun SPOT
- eDaq: Industrial strength ADC board
- eBones: Basic interface board application note
- eSPOT: Main Sun SPOT board
Our wiki for the hardware is http://wiki.java.net/bin/view/Mobileandembedded/SpotHardware.
SPOTs run Squawk, an open source Java virtual machine (VM). The download (and more information) for Squawk is https://squawk.dev.java.net/. The SPOT specific libraries can be downloaded from https://spots-libraries.dev.java.net/ along with community applications https://spots-applications.dev.java.net/
Other Lists of Semi-Open Projects
- UHF FM BUG with ButtonCell battery ( http://www.elektronika.ba/el.sheme/?akc=daj_shemu&idshema=490 ) "This bug is 100% made from an old Nokia GSM phone! It operates at 434 MHz and reception can be achieved on a modified TV tuner or 70cm band HAM radio."
- microcontroller alternatives lists a bunch of "small PCBs" (is there a better name?) designed for hacking and prototyping, that already have the processor and a few other super-common things built in ... so you don't have to start *completely* from scratch.
- ThinkCycle "ThinkCycle is a ... non-profit initiative ... supporting distributed collaboration towards design challenges facing underserved communities and the environment. ThinkCycle seeks to create a culture of open source design innovation"
- Are the Positron projects "open" enough to be mentioned? I especially liked the "Lasercut Acrylic Casebuilding Tutorial" .
- Is the Vislab puck suitable for this list?
- PICList & JAL_List free PCB contest "this will encourage people to publish designs and get more good ideas out into the real world for everyone to see." (So, are these "open" circuits?)
- http://ePanorama.net/ has a bunch of schematics and a web discussion forum. Are they "open" enough to mention here?
- "Yet Another One-hand Keyboard" ( http://chordite.com/ ) "The firmware included in the download lets an Atmel AVR '2313 microcontroller interpret chords and talk to a PS/2 port." -- it's not completely open, but the license allows you to immediately download, for free, lots of technical information and a license to build up to 5 of your own. Building more than 5 requires some sort of payment to license the patent on the hardware configuration. (The software appears to be open source). There seems to be an associated Yahoo mailing list. What is an appropriate way to invite John W. McKown and others on the mailing list to use a wiki such as Open Circuits to maintain a FAQ?
- FC's Electronic Circuits ?
- "Pandemic Ventilator Project" asks: "Does Open Source Hardware Development Work?"
- GSM SMS Controllers ( http://www.elektronika.ba/projekti/?akc=daj_projekt&idprojekt=6 ) "TwoWay Thing (GSM Controller v3) is a device that allows you to control appliances using SMS messages. There are also 4 inputs for connecting sensors so the device will send an alarm SMS or even call you to report an alarm condition. The device draws very little current and is being powered by phone’s battery which is a great thing. Nokia should be constantly charged or supplied with some sort of external power for long term operation."
- Phone-call alarm alert ( http://www.elektronika.ba/projekti/?akc=daj_projekt&idprojekt=7 ) "After programming just supply power to the device. After pressing the button "Pokreni dojavu alarma" it will start to dial (tone or pulse, depending on the jumper setup). When the phone call is succesfully established, the called party should press pound key "#" to stop the device from calling another number or again."
- SMS Box ( http://www.elektronika.ba/projekti/?akc=daj_projekt&idprojekt=9 ) "This device acts as interface between your microcontroller project and a GSM phone. It handles all modem data communication between the GSM phone and your micro-project. The best thing is that it decodes PDU into TEXT on the fly!"
- GSM alarm alert - call ( http://www.elektronika.ba/projekti/?akc=daj_projekt&idprojekt=5 ) "Alerting alarm over via GSM network"
- Bug Labs: A startup is readying a modular, open source hardware/software system resembling a set of electronic Legos. Nov. 05, 2007 
- PIC flow meter and instrumentation modules: Sensors, Gauges, Flow meter, data logging, connected by Grundfos Pumps inc. GENIbus over RS485.
- Raphaël Assénat has posted several electronics projects, including schematics. Several of them involve interfacing various "classic" video game controllers to USB. His "Caller Id decoder" is a nice example of adding just one more feature to something using a minimum of additional electronics.
- Grand Idea Studio -- do these badges count as "open circuits"?
May or may not be open, not much review material here, noted for the record, may be promoted in the future if they are outstanding in any way.