Societa Italiana Telecomunicazioni Siemens S.p.a.

Italtel Societa Italiana Telecomunicazioni S.p.a.

Italtel S.p.a.

Italtel Societa Italiana Telecommunicazioni S.p.a.

Anes Sbuelz

Francesco Marchelli

A tone generator for a telecommunication--especially telephone--system operating in the PAM/TDM mode comprises two complementary transistors with interconnected emitters joined to a 'hot' conductor of a two-wire transmission path forming part of a trunk line between two groups of subscribers, the collectors of these transistors being connected through respective series resistors to a positive and a negative terminal of a DC source. These collectors are further coupled via respective shunt condensers to the 'cold' conductor of the transmission path which is grounded through a low-ohmic further resistor. A local oscillator supplies a sinusoidal voltage wave through an operational amplifier to the interconnected bases of the two transistors whereby one or the other transistor conducts upon simultaneous closure, during a time slot assigned to a called subscriber, of a trunk switch at the near end and of a line switch at the far end of the transmission path enabling the resonant discharge of one of the previously charged shunt condensers into a remote line capacitor. Residual energy remaining stored on the parasitic capacitance of the two conductors is dissipated in a subsequent guard interval, upon the reopening of the two switches, as the partly discharged shunt condenser is recharged through the grounding resistor.

Tone generator for PAM/TDM telecommunication system

To measure electrical characteristics of a line segment, a switch or some other circuit element of a time-sharing telecommunication network using pulse-amplitude modulation, a transmission path is established between two subscriber lines through the circuit element to be tested, these subscriber lines being respectively connected to a generator of a sinusoidal test signal and to a highly sensitive signal detector. The two subscriber lines are briefly closed during a single sampling interval, or during two consecutive sampling intervals separated by an intervening guard interval during which capacitively stored residual energy is dissipated, depending on the nature of the test.

Method of and system for measuring electrical characteristics of circuit

A plurality of binary counters, each consisting of a primary and a secondary counting chain, are stepped by respective trains of clock pulses of like cadence but indeterminate phase relationship. The several primary counting chains are provided on their input sides with respective correlation circuits and on their output sides with respective sync generators, either of which is used for a concurrent restarting of both chains upon the attainment of a full count. A selection signal establishes one of the primary counting chains as the master by unblocking its sync generator while blocking its correlation circuit, the opposite being the case in all the other counters which are controlled from the unblocked sync generator through their respective correlation circuits. The primary and secondary chains of each counter work into a common comparator which detects any disparity in their readings and, in the event of such disparity, emits an alarm signal while also modifying the selection signal to designate a different primary chain as the master.

Circuit arrangement for correlating several isofrequentially stepped

Three or more oscillators to be locked in phase with one another are interconnected in a closed ring and have individual feedback loops including respective frequency dividers designed to keep them in step with a synchronizing frequency, equal to a fraction of their own operating frequency, fed in through an associated multiplexer. The multiplexer has a first input receiving the stepped-down feedback frequency of the immediately preceding oscillator, a second input connected to the output of the associated frequency divider, and a third input energizable with an external reference frequency such as a carrier of a PCM of FDM system. Each multiplexer, in the absence of an external switching command which holds it on its third input, stands on its first input unless a control circuit associated with the immediately preceding oscillator detects a disparity between the two frequencies fed to that preceding oscillator via the feedback loop and the multiplexer of the latter. In the event of such a disparity, indicating a malfunction of the oscillator associated with the control circuit detecting same, the multiplexer associated with the next-following oscillator is switched onto its second input to transform the phase-locking ring into an open-ended cascade, with emission of an alarm signal identifying the defective oscillator. Each frequency divider is provided with a self-checking circuit emitting a different alarm signal in the event of a malfunction thereof.

Malfunction detector for a group of cyclically interconnected

A sampling gate of a TDM telephone system, designed to connect a subscriber station to a trunk line during an allocated time slot, comprises a pair of bucking transistors of the same conductivity type (NPN) inserted between a live wire from the station and a corresponding 'hot' conductor of the trunk line whose 'cold' conductor, tied to the reference wire of the subscriber line, is grounded through an elevated resistance. During the allocated time slot, the two bucking transistors are rendered conductive by a timing pulse applied across their base/emitter circuits via a transformer while a connection leading from their bases to negative biasing potential is temporarily severed by an interposed FET which is cut off by the timing pulse applied to its gate electrode via a differentiation circuit.

Sampling gate for TDM telecommunication system

A coaxial cable of the type comprising a litz wire with individually enameled strands as an inner conductor and a wire plait as an outer conductor is spliced to a coaxial connector by exposing a top of the inner conductor and stripping part of the insulation from the outer conductor to expose a portion thereof set back from the tip of the inner conductor. Before splicing, the stripped cable extremity is immersed in a solvent for the enamel such as sulfuric acid, then subjected to ultrasonic vibration in a bath containing alcohol or fluorinated hydrocarbons, and thereafter immersed in a solution of tin. After neutralization and drying, the conductor portions so treated are joined to corresponding conductors of the coaxial connector whereupon a sleeve is placed around the joint and crimped to secure the connector to the cable.

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Milan, Italy

Anes Sbuelz