Abstract: A multi-frequency encoder unit is provided for a mobile radio transmitter which is constructed as a single unitary package comprising a keyboard, a first printed circuit board positioned adjacent to the rear face of the keyboard and which includes a switching circuit for providing connections from the individual keys of the keyboard to a row of connector pins on the first printed circuit board, a second printed circuit board containing the encoder circuit positioned adjacent to the first printed circuit board and electrically connected thereto by way of the connector pins which are received in connector holes in the second printed circuit board, and which includes a relay inside the encoder which causes the transmitter to be energized only as the pushbuttons of the keyboard are operated, and to be de-energized when the pushbuttons are not operated.

Abstract: A touch-tone encoder unit is provided for a mobile radio transmitter which is constructed as a single unitary package comprising a keyboard, a first printed circuit board positioned adjacent to the rear face of the keyboard which includes a switching circuit for providing connections from the individual pushbuttons of the keyboard to a row of connector pins on the first printed circuit board, a second printed circuit board containing the encoder circuit positioned adjacent to the first printed circuit board and electrically connected thereto by way of the connector pins which are received in connector holes in the second printed circuit board, and a housing attached to the keyboard and serving to sandwich the printed circuit boards between it and the keyboard in a unitary assembled condition.

Abstract: A Touch-Tone encoder unit for a mobile radio transmitter, or the like, is provided, which includes a keyboard and an encoder generator connected thereto which generates two distinct tones whenever a particular button on the keyboard is depressed and which identify the particular button. The dual tones are transmitted to appropriate receiving equipment where they are decoded, so that by depressing a number of pushbuttons on the keyboard in a particular sequence, a call may be placed. The unit of the invention may include a timing circuit which limits the length of each dual tone generated by the encoder generator to make the duration of each dual tone independent of the length of time the individual pushbuttons are depressed, the actual duration of the individual dual tones being sufficiently short so as to reduce the error rate substantially, especially where the radio transmission path is poor.