Multiple Transmitters (Figure 3) Each transmitter comes factory programmed with random codes. 2-channel transmitters have 2 different random codes, one per button, 3-channel transmitters have 3 different random codes and 4-channel transmitters have 4 different random codes, one per button. Transmitters that are purchased separately as accessories have random codes that must be changed in order to match the code of the "active" transmitter, which you are alredy using. Below are instructions for transferring an active code from a button on one transmitter to a button of your choice on another transmitter. Connect the transmitter with active code to the new transmitter using the programming connector (fig. 3A). Press and hold the selected channel button on the transmitter with the active code (fig. 3B). The light in the transmitter illuminates. Press and hold the respective channel button on the new transmitter (fig. 3C). The light in the transmitter initially starts blinking and then illuminates continuously after 1-2 sec. Code transfer is completed. Programming connector can be removed and both transmitters can now be used to operate the same door. Note: For multi-button transmitters, be sure to carry out this procedure for all the buttons you desire to use.