. The Bell System technical journal . t of obtaining the proper timing pulses with which to perform this lifunction. In a practical commercial system timing information at a [repeater would probably be derived from the incoming signal pulses. There are a number of problems involved in this recovery of timing pulses. These are being studied at the present time but were avoided in the experiment described here by deriving such information from the local synchronizing gear. Since the device we are dealing with only partially regenerates pulsesit is not enough to study the performance of a single
. The Bell System technical journal . t of obtaining the proper timing pulses with which to perform this lifunction. In a practical commercial system timing information at a [repeater would probably be derived from the incoming signal pulses. There are a number of problems involved in this recovery of timing pulses. These are being studied at the present time but were avoided in the experiment described here by deriving such information from the local synchronizing gear. Since the device we are dealing with only partially regenerates pulsesit is not enough to study the performance of a single unit — we should•like to have a large number operating in tandem so that we can observewhat happens to pulses as they pass through one after another of theseTegenerators. To avoid the necessity of building a large number of unitsthe pulse circulating technique of simulating a chain of repeaters wasj employed. Fig. 2 shows this circulating loop in block form. 70 THE BELL SYSTEM TECHNICAL JOURNAL, JANUARY 1956 HYBRID JUNCTION NO. 3. CW OSCILLATOR (4 KMC) TRAVELING WAVE AMPLIFIER (NOISE GENERATOR) Fig. 2 — The circulating loop. To provide RF test pulses for this loop the output of a 4 kmc, cwoscillator is gated by baseband pulse groups in a microwave gate ormodulator. The resultant microwa\-e pulses are fed into the loop (heavyline) through hybrid junction No. 1. They are then amplified by a trav-eling-wave amplifier the output of which is coupled to the pulse regen-erator through another hybrid junction (No. 2). The purpose of thishybrid is to provide a position for monitoring the input to the regen-erator. A monitoring position at the output of the regenerator is pro-vided by a third hybrid, the main output of which feeds a considerablelength of waveguide which provides the necessary loop delay. At the farend of the waveguide another hybrid (No. 4) makes it possible to feednoise, which is derived from a traveling-wave amplifier, into the combined output after pass
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