Horizontal sync signal is applied as a reference pulse signal to a first input terminal of a phase detector and is also applied as a gating pulse to a gate circuit. Output of a frequency divider which divides the frequency of the output of a VCO is applied as a comparison pulse to a second input terminal of the phase detector. In the phase detector, a phase detection pulse having a pulse width proportional to the phase difference between the reference pulse and the comparison pulse is obtained. This phase detection pulse is applied through a buffer to a gate circuit. In the gate circuit, the current path from the phase detection pulse input terminal to the output terminal is held conductive during the period of the gating pulse, and during this period an output pulse containing as a component thereof the phase detection pulse mentioned above is obtained. This output pulse is smoothed through a filter to be applied as an oscillation frequency control voltage input to the VCO.

A television horizontal deflection synchronizing system uses two phase-lock loops. A horizontal oscillator operating at a frequency greater than the horizontal frequency is counted and a bilevel signal near the horizontal frequency is generated. A first phase-lock loop having a relatively long time constant controls the oscillator to maintain the bilevel signal in frequency and phase synchronism with horizontal synchronizing signals. In order to compensate for load-dependent variations in the delay of the horizontal deflection stage, a second phase-lock loop is used. The second phase-lock loop includes a phase detector, one input of which is coupled to an output of the first phase-lock loop and a second input of which is coupled to the deflection circuit for responding to the retrace pulse for enabling the phase detector to produce a current of a first polarity when the bilevel signal has a first value and a current of a second polarity when the bilevel signal has a second value. A loop filter is coupled to an output of the phase detector for filtering the first and second polarity currents to form a control signal. A phase controllable source includes a control input coupled to the loop filter for producing horizontal-rate drive pulses at a time which makes the retrace pulses synchronous with the bilevel signal.

A circuit arrangement for amplifying a periodic signal and for adjusting a reference level contained therein, in which a charging/discharging arrangement alternately supplies charging or discharging currents to a storage means, depending on whether the value of a periodic signal exceeds or is exceeded by a limit value, such that a mean value at least substantially corresponding to the reference level occurs at the storage means includes a compensator means which adjusts the charging and disharging currents by a compensation factor which is selected such that the ratio of the charging current to the discharging current is independent of fluctuations in current resulting from variations affecting the gain factors of amplifier components comprised in the amplifier means.

A concentration of microbiocides added to fluid systems is monitored by a fluorescence emission method which is based upon the measurement of the fluorescence intensity of an inert fluorescent additive which is added to the microbiocide composition prior to its introduction into the fluid system. Optionally, the fluorescent additive may be metered separately into the fluid system in direct proportion to the amount of industrial microbiocide added. Biocide compositions containing inert fluorescent additives are also disclosed. Preferably the fluid system is an industrial aqueous system. Preferred combinations of biocide and fluorescent additive are glutaraldehyde/1,5-naphthalene disulfonic acid, glutaraldehyde/1,3,6,8-pyrene tetrasulfonic acid, isothiazolone/1,5-naphthalene disulfonic acid, isothiazolone/1,3,6,8-pyrene tetrasulfonic acid, glutaraldehyde/fluorescein, alkyl-dimethylbenzyl ammonium chloride quaternary/2-naphthalene sulfonic acid and 2-(decylthio)-ethanamine/2-naphthalene sulfonic acid.

A single antenna, dual frequency transponder is provided. The transponder includes the antenna, first and second capacitors, a microprocessor/coder for generating a first and second control signals, and a logic circuit which uses the two control signals as inputs and depending on the state of the second control signal either provides an open circuit or a frequency signal at its output node. When the second control signal is a dormant (inhibit) signal, an open circuit is provided. As a result, the capacitors and the antenna provide a first tuned LC circuit which will receive an incoming signal at a desired first frequency. The incoming signal thereby resonates the LC circuit which provides a wake-up signal to the microprocessor/coder. In turn, the microprocessor/coder generates the first control signal of a desired second frequency. In turn, the logic circuit provides a related signal of the same second frequency as an output. With such an output, one of the two capacitors is effectively eliminated from the circuit, and the remaining capacitor and the antenna constitute a second tuned LC circuit which is tuned to the second frequency. By providing adjustable capacitance capacitors, the circuit is adjustable to desired incoming and outgoing frequencies.