Please note: please do not confuse this black-coloured, white-button model containing a large 9V battery, with the model number 4330EML (blue casing with white buttons and a small 12V battery), which is not compatible. It should also not be confused with the model CHAMBERLAIN 751E, which has the same frequency but which has internal programmable switches. The frequency of this remote control is 27.145 MHz.