Data transmission over voice bandwidth of FM radio channel

Claim 2

A data transmission system located at a remote location for transmitting digital data produced at the remote location to a central station and receiving digital data in the form of modulated tone transmitted from said central station, said system comprising: a remote terminal unit; a frequency modulated radio transceiver having both a receiver and transmitter circuit, said transmitter circuit having first circuit means for frequency modulating its transmitted carrier free of pre-emphasis with a relatively flat deviation versus modulating frequency characteristic and minimal phase delay distortion, said first circuit means being coupled to said remote terminal unit; a power supply, said power supply being permanently coupled to the initial stages of the transmitter circuit including said first circuit means said receiver circuit being coupled to said power supply to receive signals transmitted to said remote location from said central station; a modem, said modem being coupled to said remote terminal unit and designed to convert the digital data produced at said remote location to a modulated tone, said modem being coupled to said first circuit means of the transmitter whereby said modulated tone modulates the transmitter frequency; the modem in addition being coupled to the receiver circuit to convert a modulated tone received from said central station into digital command signals, said digital command signals being supplied to said remote terminal unit to control said remote terminal unit; and a second circuit means, said second circuit means being coupled to said remote terminal unit and disposed to couple said power supply to the final transmitting stages of said transmitter, said remote terminal unit actuating said second circuit means in response to one of said digital command signals.

Claim 3

The data transmission system of claim 1, wherein said second circuit means comprises two relays, the first relay being a sensitive power relay disposed to operate the second relay, said second relay being a fast acting power relay.

Claim 4

A data transmission system for transmitting digital data in the form of modulated tone from a central facility to a plurality of offshore production platforms and transmitting digital data produced at said plurality of platforms to said central facility, said system comprising: a frequency modulated radio transceiver at each platform, all of said transceivers having the same transmit and receive frequency, said transceivers in addition having transmitting and receiving portions, said transmitting portion having an input circuit means for frequency modulating the transmitted carrier frequency free of pre-emphasis and a flat deviation versus modulating frequency characteristic and minimal relative phase delay; a remote terminal unit at each platform coupled to both the transmitter and receiver portion of said transceiver, said remote terminal unit including a modem for translating digital data produced on said platforms to a modulated tone and converting a modulated tone received from said central facility to digital data, the modulated tone produced by said modem being supplied to said input circuit means; a power supply at each platform, said power supply being coupled to the receiver portion of said transceiver and the initial stages of the transmitter including said input circuit means; a switch circuit, said switch circuit being disposed to couple said power supply to the remaining portion of the transmitter portion of said transceiver, said switch circuit being coupled to and actuated by said remote terminal unit in response to a modulated tone received from said central facility; the receiver portion of said transceiver being coupled to said remote terminal unit to supply said modulated tone received from said central facility to said remote terminal unit to operate said modem to supply said modulated tone to said input circuit means in response to said modulated tone; and a transceiver at said central facility having the same transmit frequency as the receivers on said platforms whereby said central facility can contact all of said platforms.

Claim 5

A data transmission system for transmitting digital data in the form of modulated tone from a central facility to a plurality of offshore production platforms and transmitting digital data produced at said plurality of platforms to said central facility, said system comprising: a frequency modulated radio transceiver at each platform, all of said transceivers having the same transmit and receive frequency, said transceivers in addition having transmitting and receiving portions, said transmitting portion having an input circuit means for frequency modulating the transmitted carrier frequency free of pre-emphasis and a flat deviation versus modulating frequency characteristic and minimal relative phase delay; a remote terminal unit at each platform coupled to both the transmitter and receiver portion of said transceiver, said remote terminal unit including a modem for translating digital data produced on said platforms to a modulated tone and converting a modulated tone received from said central facility to digital data, the modulated tone produced by said modem being supplied to said input circuit means; a power supply at each platform, said power supply being coupled to the receiver portion of said transceiver and the initial stages of the transmitter including said input circuit means; a switch circuit, said switch circuit being disposed to couple said power supply to the remaining portion of the transmitter portion of said transceiver, said switch circuit being coupled to and actuated by said remote terminal unit in response to a modulated tone received from said central facility; the receiver portion of said transceiver being coupled to said remote terminal unit to supply said modulated tone received from said central facility to said remote terminal unit to operate said modem to supply said modulated tone to said input circuit means in response to said modulated tone; and a transceiver at said central facility having the same transmit frequency as the receivers on said platforms whereby said central facility can contact all of said platforms.