Interstation synchronization apparatus

Claim 2

Interstation synchronization apparatus for time division multiplex communication systems, said apparatus including multiinput phase-controlled oscillator means comprising at lease one phase comparator means and variable frequency oscillator means, said at least one phase comparator means being adapted to receive first and second input signals and produce in response thereto an output signal representative of the phase difference therebetween, said first input signal being representative of an externally generated synchronization signal and said second input signal being representative of the output of said variable frequency oscillator means, said variable frequency oscillator means producing an output signal having a frequency determined by signals applied to a control input terminal thereof; the improvement comprising: signal adder means having a plurality of inputs thereto electrically interposed between said at least one phase comparator means and said control input terminal of said variable frequency oscillator means, said signal adder means thereby being adapted to receive the output of said at least one phase comparator means at one of said plurality of inputs thereto and apply a control signal to said control input terminal of said variable frequency oscillator means; and signal generator means operably connected to a second input of said signal adder means, said signal generator means being adapted to apply a signal to said second input of said signal adder means for compensating for a predetermined delay present in said first input signals applied to said phase comparator means.

Claim 3

The apparatus of claim 1, the improvement additionally comprising feedback means directly connecting information representative of the output of said variable oscillator means to said phase comparator means to provide said second input signals thereto.

Claim 4

The apparatus of claim 2, the improvement additionally comprising low-pass filter means electrically interposed between the output of said at least one phase comparator means and said one of said plurality of inputs to said signal adder means.

Claim 5

The apparatus of claim 2, the improvement further comprising: additional phase comparator means, said additional phase comparator means each being adapted to receive first and second input signals and produce in response thereto an output signal representative of the phase difference therebetween, said first input signal to each of said additional phase comparator means being representative of an externally generated synchronization signal and said second input signal being representative of the output of said variable frequency oscillator means; and means for combining the output signals of each of said phase comparator means and applying said combined signals to said one of said plurality of inputs to said signal adder means.

Claim 6

The apparatus of claim 4, wherein said signal combining means comprises weighted averaging circuit means whereby each of said output signals are individually weighted prior to their combination by the averaging portion of said weighted averaging circuit means.

Claim 7

The apparatus of claim 5, the improvement additionally comprising low-pass filter means electrically interposed between the output of said weighted averaging circuit means and said one of said plurality of inputs to said signal adder means.

Claim 8

In an interstation clock synchronization network for time division multiplex communication systems having a plurality of communication stations, said network including multi-input phase controlled oscillator means located at each station, each of said multi-input phase-controlled oscillator means located at each station comprising at least one phase comparator means and variable frequency oscillator means, said at least one phase comparator means being adapted to receive first and second input signals and produce in response thereto an output signal representative of the phase difference therebetween, said first input signals being representative of the output of a variable frequency oscillator means present at a remotely located communication station within the time division multiplex communication system and said second input signal being representative of the output of said variable frequency oscillator means located at the same station within the time division multiplex communication system, said variable frequency oscillator means producing a synchronization signal whose frequencies are determined by signals applied to a control input terminal thereof; the improvement comprising: signal adder means located at each station having a plurality of inputs thereto electrically interposed between said at least one phase comparator means and said control input terminal of said variable frequency oscillator means, said signal adder means thereby being adapted to receive the output of said at least one phase comparator means at one of said plurality of inputs thereto and apply a control signal to said control input terminal of said variable frequency oscillator means; and signal generator means located at each station operably connected to a second input of said signal adder means, said signal generator means being adapted to apply a signal to said second input of said signal adder means for compensating for delays present in said first input signals to said phase comparator means.

Claim 9

In an interstation clock synchronization network for time division multiplex communication systems having a plurality of communication stations, said network including multi-input phase controlled oscillator means located at each station, each of said multi-input phase-controlled oscillator means located at each station comprising at least one phase comparator means and variable frequency oscillator means, said at least one phase comparator means being adapted to receive first and second input signals and produce in response thereto an output signal representative of the phase difference therebetween, said first input signals being representative of the output of a variable frequency oscillator means present at a remotely located communication station within the time division multiplex communication system and said second input signal being representative of the output of said variable frequency oscillator means located at the same station within the time division multiplex communication system, said variable frequency oscillator means producing a synchronization signal whose frequencies are determined by signals applied to a control input terminal thereof; the improvement comprising: signal adder means located at each station having a plurality of inputs thereto electrically interposed between said at least one phase comparator means and said control input terminal of said variable frequency oscillator means, said signal adder means thereby being adapted to receive the output of said at least one phase comparator means at one of said plurality of inputs thereto and apply a control signal to said control input terminal of said variable frequency oscillator means; and signal generator means located at each station operably connected to a second input of said signal adder means, said signal generator means being adapted to apply a signal to said second input of said signal adder means for compensating for delays present in said first input signals to said phase comparator means.

Claim 10

The apparatus of claim 7, the improveMent additionally comprising feedback means located at each station directly connecting information representative of the output of the variable oscillator means located at a given communication station to said phase comparator means located at that station to provide said second input signals thereto and transmission line means located at each station for additionally applying information representative of the output of said variable oscillator means located at said given communication station to phase comparator means of at least one remotely located station to provide said first input signals thereto.

Claim 11

The apparatus of claim 8, wherein said transmission line means is connected to the same remotely located communication station within the time division multiplex communication system as supplies said first input signals to said at least one phase comparator means at said given station.

Claim 12

The apparatus of claim 9, the improvement additionally comprising low-pass filter means located at each station electrically interposed between the output of said at least one phase comparator means and said one of said plurality of inputs to said signal adder means.

Claim 13

The apparatus of claim 9, the improvement further comprising: additional phase comparator means located at certain of said communication stations in said time division multiplex communication system, said additional phase comparator means each being adapted to receive first and second input signals and produce in response thereto an output signal representative of the phase difference therebetween, said first input signals to each of said additional phase comparator means being representative of the output of a variable frequency oscillator means present at a different remotely located communication station within the time division multiplex communication system and said second input signal being representative of the output of said variable frequency oscillator means located at the same communication station within the time division multiplex communication system; and means located at each of said certain communication stations for combining the output signals of each of said phase comparator means and applying said combined signals to said one of said plurality of inputs to said signal adder means.

Claim 14

The apparatus of claim 11, wherein said signal combining means located at said certain communication stations comprises weighted averaging circuit means whereby each of the outputs from all of the phase comparator means located at said certain communication stations are individually weighted prior to their combination by the averaging portion of said weighted averaging circuit means.

Claim 15

The apparatus of claim 12, the improvement additionally comprising low-pass filter means located at each of said certain communication stations electrically interposed between the output of said weighted averaging circuit means and said one of said plurality of inputs to said signal adder means.

Claim 16

The apparatus of claim 13, additionally comprising additional transmission line means located at each of said certain of said communication stations, each of said additional transmission line means applying information representative of the output of the variable oscillator means located at a given station of said certain communication stations to phase comparator means of different remotely located stations to provide said first input signals thereto.