Synchronisation signal

TCSPC needs a timing reference signal from the light source. This is no problem for picosecond diode lasers, which deliver a trigger output pulse from the laser diode driver. For free-running solid-state lasers or jet-stream dye lasers, a suitable synchronisation signal can be generated by a photodiode. A simple solution is to use a fast PIN photodiode in one of the circuits shown in Fig. 7.42. 

The operating system provided a mechanism to overcome this problem by synchronising multiple processors using a synchronisation signal transmitted over a dedicated RS485 line. This mechanism ensures that the frames (actually, the minor frames) on each processor start at the same time, but of course, introduces a potential common point of failure. 

The construction of the optoelectronic interface can be based on a silicon photodiode since analytical and reference wavelengths are from the visible and the IR regions, respectively. The signals can be filtered out by optical filters (then two photodiodes are required) or one photodiode can be synchronised with modulation waves of the LEDs used. Finally, silica optical fibres can be used as light waveguides. The choice between single fibre or bundle is determined by the application of the sensor. 

There are also some important differences in the technology required to realise bistatic radar. In monostatic radar synchronisation between transmission and reception is done via a stable source, usually a local oscillator. In bistatic radar the separation of transmitter and receiver makes this much more difficult. An equivalent situation has to be achieved and this is done either via synchronised atomic clocks, a signal such as GPS or by reception of a reference signal received directly from the transmitter. The latter technique is typically used in PCL systems and we shall return to this later. 

The drive of the dispersing device is synchronised with the x-axis of the recorder or fed directly to a computer, so that this indicates the wavelength of radiation reaching the detector. The signal from the detector is transmitted to the y-axis of the recorder or to a computer and this indicates how much radiation is absorbed by the sample at any particular wavelength. 

The magnetic scan is synchronised with the x-axis of a recorder and calibrated to appear as mass number (strictly m/e). The amplified current from the ion collector gives the relative abundance of ions on the y-axis. The signals are usually pre-processed by a computer that assigns a relative abundance of 100% to the strongest peak (base peak). 

Figure 1 The archetypical REDOR pulse sequence. (A) rotor-synchronised S-spin-echo experiment defining the reference echo amplitude Sq the REDOR pulse sequence in (B) with the additional rotor-synchronised /-channel 7i-pulses provides the signal intensity S.

The appetite centre in the arcuate nucleus appears to be composed of at least two classes of neurons primary neurons that sense metabohte levels and regulating hormones, and secondary neurons that synchronise information from primary neurons and coordinate bodily functions through vagal signalling. There are those which stimulate appetite through secretion of NPY and the AgRP, and those which depress appetite through secretion of POMC (see also Section 3.9). 

Although the diode array detects the same material a few seconds after the mass spectrometer, the software may be programmed with this time delay so that the two signals appear to be synchronised. Also, a second synchronisation is needed for the difference in time between the component being detected by the mass spectrometer (from the split flow) and the component arriving at the fraction collector (main flow). This timing is needed to ensure that the trigger from the mass spectrometer to start... 

Fig. 12a, b STMAS pulse sequences that suppress CT CT diagonal peaks using a a soft presaturation pulse b the subtraction method. In b the receiver phase is alternated between synchronised (bl) and non-synchronised (b2) for subtraction of the CT CT signal... 

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