This mode is called “silent mode”. Connection as follows: from the machine run out 4 harnesses. 1x Power, 1x data for plotters, 1x data for PC, 1x external switch. The Wire for the external switch is 2-pole, black and purple. If the wires are shorted, i.e. are connected via a switch, then the easyTRX in pure reception mode. With this switch, then a switch between transmit / receive mode (switch is not closed) and closed pure reception operation (shaded) is possible.