Remote correlation of sequence of events

Claim 2

In a digital data acquisition system having a master station connected to a plurality of remote stations from which are gathered information as to time of occurrence, time tags, of certain events as obtained by reference to unsynchronized clocks at associated remote stations, a method for correcting a time tag so that it refers to a time as kept by a master clock at the said master station, to make possible a time ordering of events at different remote stations, comprising the steps of: transmitting from said master station to said remote stations inerrogatory messages requesting information on time tagged events at said remote stations; storing at said master station a first signal representing a master clock time, Tm(O), when the end of the interrogatory message is sent by said master station; producing at each interrogated remote station a second signal representing remote clock time, Tr(X), when the end of the interrogatory message was received at the remote station; producing at each of said remote stations a third signal which constitutes a reply message incorporating the time tag for the events information requested and said time Tr(X); storing at the master station a fourth signal for each interrogated remote station representing a master clock time, Tm(Y), when the end of the reply message is received at said master station; combining at the master said first, third, and fourth signals associated with each remote station to produce a fifth signal for each remote station representing a time correction factor, TCF, for each event indicative of the difference between the time of said master clock and the time of a corresponding remote clock with compensation for signal transmission time between said master station and said corresponding remote station, said combination being in accordance with an equation TCF=1/2[Tm(O)+Tm(Y)-]Tr(X); summing for each event said fifth signal and that part of the third signal representing the time tag to produce a sixth signal for each event representing a correct timing of the event with reference to the master clock; and recording at said master station said sixth signal for each event to provide a basis for time ordering a sequence of said events from said plurality of remote stations having unsychronized clocks.

Claim 3

In a digital data acquisition system having a master station connected to a plurality of remote stations from which are gathered information as to time of occurence, time tags, of certain events as obtained by reference to unsynchronized clocks at associated remote stations, a method for correcting a time tag so that it refers to a time as kept by a master clock at said master station, to make possible a time ordering of events at different remote stations, comprising the steps of: transmitting from said master station to said remote stations interrogatory messages requesting information on time tagged events at said remote stations; storing at said master station a first signal representing a master clock time, Tm(O), when an end of the interrogatory message is sent by said master station; producing at each interrogated remote station a second signal representing remote clock time, Tr(X), when the end of said interrogatory message is received at said remote station; producing at each of said remote stations a third signal which constitutes a reply message incorporating the time tag for the events information requested, the delay time TPTM, and the time Tr(X); storing at said master station a fourth signal for each interrogated remote station representing a master clock time, Tm(Y), when the end of the reply message is received at the master station; combining at said master station said first, third, and fourth signals associated with each remote station to produce a fifth signal for each remote station representing a time correction factor, TCF, for each event indicative of the difference between the time of said master clock and the time of a corresponding remote clock with compensation for signal transmission time between said master station and said corresponding remote station, said combination being in accordance with the equation TCF=1/2[Tm(O)+Tm(Y)-TPTM-M-Tr(X), where M is that length of said interrogatory message received which is in excess of the length of said reply message sent; summing for each event said fifth signal and that part of said third signal representing the time tag to produce a sixth signal for each event representing the correct timing of the events with reference to said master clock; and recording at said master station said sixth signal for each event to provide a basis for time ordering the sequence of said events from said plurality of remote stations having unsynchronized clocks.

Claim 4

In a digital data acquisition system having a master station connected to a plurality of remote stations from which are gathered information as to time of occurence, time tags, of certain events as obtained by reference to unsynchronized clocks at associated remote stations, a method for correcting a time tag so that it refers to a time as kept by a master clock at said master station, to make possible a time ordering of events at different remote stations, comprising the steps of: transmitting from said master station to said remote stations interrogatory messages requesting information on time tagged events at said remote stations; storing at said master station a first signal representing a master clock time, Tm(O), when an end of the interrogatory message is sent by said master station; producing at each interrogated remote station a second signal representing remote clock time, Tr(X), when the end of said interrogatory message is received at said remote station; producing at each of said remote stations a third signal which constitutes a reply message incorporating the time tag for the events information requested, the delay time TPTM, and the time Tr(X); storing at said master station a fourth signal for each interrogated remote station representing a master clock time, Tm(Y), when the end of the reply message is received at the master station; combining at said master station said first, third, and fourth signals associated with each remote station to produce a fifth signal for each remote station representing a time correction factor, TCF, for each event indicative of the difference between the time of said master clock and the time of a corresponding remote clock with compensation for signal transmission time between said master station and said corresponding remote station, said combination being in accordance with the equation TCF=1/2[Tm(O)+Tm(Y)-TPTM-M-Tr(X), where M is that length of said interrogatory message received which is in excess of the length of said reply message sent; summing for each event said fifth signal and that part of said third signal representing the time tag to produce a sixth signal for each event representing the correct timing of the events with reference to said master clock; and recording at said master station said sixth signal for each event to provide a basis for time ordering the sequence of said events from said plurality of remote stations having unsynchronized clocks.