   if(SERIAL_DEBUG) {
     Serial.begin(9600);
     Serial.println("setup");
+    Serial.print("isSource: ");
+    Serial.println(isSource);
   }
 }
 

  // assess energy supply, find shortest disance to source
  shortestDistanceToSource = 99;
  for (int i =0; i<NUM_CONN; i++) if (distanceToSource[i] < shortestDistanceToSource) shortestDistanceToSource = distanceToSource[i];

  // if we have energy, switch (or keep) lamp on, pass it on and check again in some time
  if (shortestDistanceToSource<99) {

  // check all lines for incoming data
  for (int i=0;i<NUM_CONN;i++) if(bus[i]->available()) {
    char c = bus[i]->read();
    if(SERIAL_DEBUG) {
      Serial.print(i);
      Serial.print(": ");
      Serial.println(int(c));
    }
    switch(c) {
      case ALERT: // button is pressed
        if (!isSource && !alertState) {
