ring synchronization (sync) input compatible clock input both HC-5502A

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ring synchronization (sync) input compatible clock input both HC-5502A

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Using Ring Sync with HC-5502A HC-5504 SLICs
ring synchronization (sync) input compatible clock input both HC-5502A HC-5504 SLICs. It's purpose insure that ring relay activated deactivated only when instantaneous ring voltage, which high 150V peak, near zero crossing. ring sync used, must tied high insure proper ring trip. When used, important consider which zero crossing ring voltage, positive negative, ring sync signal must synchronized with. Subsequent illustrations equations highlight this consideration. detailed description ring trip sequence events, refer Application Note Phillips. Excerpts from pertinent section included below. Ring Trip Sequence Ring Command (RC) input taken during ringing. This activates ring relay driver (RD) output providing telephone off-hook line power denial state. ring relay connects ring generator subscriber loop. ring generator output usually 80VRMS, 20Hz signal. with Harris SLIC, ring signal should exceed 150V peak. Since telephone ringer coupled, only ring current will flow. HC5502A SLIC, ring current sunk ring feed amplifier output stage whereas HC-5504 ring path flows directly into relay contacts. high impedance terminal exists HC-5504 that impedance node isolated from ring path battery referenced ring scheme. ring current flowing subscriber circuit will sensed across RB4, will give rise voltage output longitudinal amplifier. attenuate this signal before reaches ring trip detector prevent false ring trip. nominally 0.47µF increased towards short lines several telephones connected parallel across line order prevent false intermittent ring trip. When subscriber goes off-hook, path established between output winding ring generator battery ground terminal. longitudinal imbalance established since feed current flowing through feed resistors. longitudinal amplifier output driven negative. Once exceeds ring trip threshold ring trip detector, logic circuitry driven trip ring relay establishing off-hook condition such that will become active loop metallic current starts flow. Figure illustrates sequence events during ring trip with ring synchronization. Note, that owing phase shift introduced pass filter (R19, pulse will occur most negative point attenuated ring signal that into ring trip detector. Hence, when conditions established RTD, component actually assists ring trip taking place. ring synchronization used, then should held permanently logic high nominally: ring trip will occur asynchronously with respect ring voltage. Ring trip guaranteed take place within three ring cycles after telephone going off-hook.
FIGURE RING TRIP SEQUENCE
Copyright
Harris Corporation 1998
Application Note Case HC-5502A Injected Ringing
(IRING ITIP) (RB4) (During Ringing ITIP (IRING) (RB4) IRING (VRF VRING)/RB4 (VRF VRING)
Case HC-5504 Ring Injected Ringing
(IRING ITIP) (RB4) (During Ringing ITIP (IRING)(RB4) IRING (VRFS VRING)/RB4 (VRFS VRING)
FIGURE
FIGURE
FIGURE
FIGURE
Case refer Figures this situation desired result obtained, namely, that ring sync occurs during negative peak VC4. This helps achieve ring trip faster because, once subscriber goes off-hook, negative shift observed VC4. This shift approaches comparator threshold ring trip detection circuit. negative peak VC4(AC) precedes negative going shift VC4, achieve ring trip shorter time frame. Also this configuration allows ring trip occur long lines, order 3000. these line lengths, negative shift will never reach threshold because there enough current through sense resistor, RB4. However, negative peak (AC) will cross ring trip detector comparator threshold ring trip will occur. Conclusion this case make sure ring sync synchronized with negative zero crossing VRING appears line.
Case refer Figures Here ring sync must synchronized with positive zero crossing VRING (AC) appears line coincide with negative peak (AC), previous case. from Figure that ring sync negative zero crossing would coincide with positive peak inhibiting ring trip loops greater than approximately 800. Conclusion this case make sure ring sync synchronized with positive zero crossing VRING (AC.). other ring configurations, namely, injected balanced ringing HC-5504, ring sync used, must synchronized with negative zero crossing VRING(AC).
Acknowledgment
author wishes thank Geoff Philliips contribution this paper.

ring synchronization (sync) input compatible clock input both HC-5502A

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