What did CCTV mean?

diagram of a CCTV circuit for controlling a welding robot arm. "Closed Circuit TV System Automatically Guides Welding Arc" includes various labels for parts of the system and circuit.

"Closed-Circuit Transmission Closed-circuit transmission provides a means whereby television materials can be distributed over cables to specific groups with recievers directly connected to the wired system. Only television receivers connected to the closed-circuit cable can receive the television information. If the cable is extended throughout a building or campus, every television set connected to it would be able to receive the television channels that are placed on the cable."

"3-3-74: We tried something interesting today. I found a ladybug on the playground, and we decided to watch the bug under A's camera lens. It proved to be quite exciting, and we could see the bug so clearly. F came to our room today. I let her play some of the word games by herself. I wanted to see if she could work independently on the CCTV. She can work by herself and she remembers to watch the monitor while she reads and writes."

"Fig 1.1 A simple CCTV system" diagram shows "Light Subject Camera Lens Coaxial cable Monitor"

"3-19-74: I let E maneuver the room camera—she always feels so good about herself when she has a responsibility and can run the control box. 3-21-74: We showed a group of visitors some of the things we do using the CCTV. We had some good group activities using our clocks. I had the class fill in the correct time after viewing a clock. They did very well. 3-22-74: I was absent, but the class helped the substitute use the CCTV. They showed her how to focus the lens and which buttons to push. I feel they can work independently now, and they are able to maneuver their own system."

I think the closed-circuit technical limitations of the original CCTV contributed to a sort of safety and intimacy. Without the leaky indeterminacy of contemporary cloud-networked surveillance apparatuses, CCTV held potential as a playful tool of individual agency and control. A closed-circuit meant the TV did not go beyond clear boundaries – “their own system”.

"12-3-73: We tried a great lesson. I brought in labels from some cans and jars. I enlarged them enough so the class could read them. I'll bet they never were able to read them before—these machines are fantastic. Anyway, we discussed the contents and ingredients. I asked them to find the weight in ounces. Afterward, we drew pictures of the labels, and I'm going to have them paste them on their own cans. They enjoyed this."

diagram of a screen displaying "CCTV" label says "(b) monitor display"

A proposal for a new Closed-Circuit Guarantee:

A kite mark for CCTV systems awarded through a form of accreditation and audit, which promises that the video and sound captured by a camera system are not transmitted beyond the closed circuit of the current context. By processing video ‘locally’ rather than transmitting it via a network to remote servers, a Closed-Circuit Guaranteed camera system could enact locally defined and audited controls before storing video. For example a library might wish to ensure that no children are recorded in their video archives and a CCTV-guarantee system could detect and edit out any such images before storage.

diagram of a CCTV system. "1-6 The 'Dedicated' single-camera/single-monitor CCTV setup. Burle/RCA" shows "Camera -> Time-lapse video cassette recorder -> Monitor"

Here is a quick prototype test for a camera system in which all the CCTV cameras are programmed to try to edit out a subject (in this test detection of the colour red is used as a quick stand-in for more nuanced automatic editing such as removing all images of children from the video before they are recorded):

"3-27-74: I let the class use the puppets during reading. We've been reading a story about a giant and some magicians so the class wanted to act out certain parts of the book. I used the CCTV room camera to focus on the puppet stage, and some of the students preferred to watch the show via their own monitor."

This is a view of the red puppet moved through the CCTV cameras as their code tries to ensure that the recordings are edited correctly:

"Industrial and Commercial CCTV (Principles and Circuits)"

// a quick red-detection editing hack largely using example code from teaching by Daniel Shiffman
// his teaching is at
// support him at
// based on code for:


Movie[] vids;

color trackColor; 
int screen = 0;
boolean recording = false;

void setup() {
  size(640, 360); 

  Movie.supportedProtocols[0] = "rtsp";
  vids = new Movie[]{ 
    new Movie(this, "rtsp://user:passphrase@192.168.1.x1:xxx/stream2"), 
    new Movie(this, "rtsp://user:passphrase@192.168.1.x2:xxx/stream2"), 
    new Movie(this, "rtsp://user:passphrase@192.168.1.x3:xxx/stream2"), 
    new Movie(this, "rtsp://user:passphrase@192.168.1.x4:xxx/stream2"), 
    new Movie(this, "rtsp://user:passphrase@192.168.1.x5:xxx/stream2"), 
    new Movie(this, "rtsp://user:passphrase@192.168.1.x6:xxx/stream2"), 
  for (Movie vid : vids) {;

  trackColor = color(120, 11, 45);

void movieEvent(Movie video) {;

void draw() {
  for (int m = 0; m < vids.length; m++) {

    // Before we begin searching, the "world record" for closest color is set to a high number that is easy for the first pixel to beat.
    float worldRecord = 500; 

    // XY coordinate of closest color
    int closestX = 0;
    int closestY = 0;

    // Begin loop to walk through every pixel
    for (int x = 0; x < vids[m].width; x++ ) {
      for (int y = 0; y < vids[m].height; y++ ) {
        int loc = x + y * vids[m].width;
        // What is current color
        color currentColor = vids[m].pixels[loc];
        float r1 = red(currentColor);
        float g1 = green(currentColor);
        float b1 = blue(currentColor);
        float r2 = red(trackColor);
        float g2 = green(trackColor);
        float b2 = blue(trackColor);

        // Using euclidean distance to compare colors
        float d = dist(r1, g1, b1, r2, g2, b2); // We are using the dist( ) function to compare the current color with the color we are tracking.

        // If current color is more similar to tracked color than
        // closest color, save current location and current difference
        if (d < worldRecord) {
          worldRecord = d;
          closestX = x;
          closestY = y;

    // We only consider the color found if its color distance is less than 10. 
    // This threshold of 10 is arbitrary and you can adjust this number depending on how accurate you require the tracking to be.
    if (worldRecord < 10) { 
      // Draw a circle at the tracked pixel
      ellipse(closestX, closestY, 16, 16);
    } else {
      screen = m;
  image(vids[screen], 0, 0, width, height);
  if (recording==true) {

float distSq(float x1, float y1, float z1, float x2, float y2, float z2) {
  float d = (x2-x1)*(x2-x1) + (y2-y1)*(y2-y1) +(z2-z1)*(z2-z1);
  return d;

void mousePressed() {
  // Save color where the mouse is clicked in trackColor variable
  int loc = mouseX + mouseY*vids[screen].width;
  trackColor = vids[screen].pixels[loc];
  println(red(trackColor), green(trackColor), blue(trackColor));

void keyPressed() {
  recording = !recording;

diagram: "1-7 CCTV pan/tilt mechanisms and Zoom lenses. Burle/RCA" showing "Camera with zoom lens Pan/tilt mount Monitor Pan/tilt control Zoom lens control"

– Ben Dalton