ZETRON 640 DAPT XTRA, Руководство по установке и ремонту

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Hardware Overview
24 025-9416
MODEL 640 DAPT XTRA
TRUNK A TRUNK B TRUNK C TRUNK D
READY
COM
MODEM
LINE
ANS
ACT
ANA PTT
DIG PTT
BUSY
AGC KILL
FROM TEL
BAL R
BAL C
Figure 7. Model 640 DAPT XTRA Front Panel
Notes On Figure 7:
1. The trunk LEDs (ACT, ANS, and LINE) are identical for each of the four available trunks.
2. The adjustment pots are identical for each of the four available trunks, but the AGC KILL switch is on
the outside of the associated pots (above the top banks, and below the bottom banks). The four upper
adjustments on the left bank define audio for trunk C; the lower four define audio for trunk D. The four
upper adjustments on the right bank define audio for trunk A; the lower four define audio for trunk B.
3. The floppy disk drive shown is optional. The slot is covered when no disk drive is installed.
The AGC KILL (automatic gain control) switch adjusts voice audio levels on the telephone inter-
face line. The AGC compensates for the call-to-call changes in the loudness of the caller’s voice
and the gain of each phone call. The voice audio signal is appropriately amplified and then fed to
an envelope detector, modem, DTMF detector, and CODECs for each trunk.
The FROM TEL adjustment controls silence deletion in the audio provided on the telco trunk.
Generally, silence deletion is increased by turning the pot counterclockwise.
The BAL R and BAL C pots effectively cancel out the outgoing audio from the incoming audio
(that is, “sidetone”). Full-duplex hybrids separate the incoming and outgoing audio. The two
balance controls are used to “match” the hybrid to the telephone lines. A better impedance match
yields less reflected impedance and improved audio isolation.
DID Trunk Configuration
The DID configuration, illustrated in Section 11 (Part No. 024-0076), provides a balanced 48V
DC
battery current with full-duplex hybrid audio signaling to the TIP1 / RING1 pair of the telco
interconnect. A loop closure at the telco CO or PABX is sensed by the resistor bridge and tran-
sistor circuitry, which drives the loop detect opto-isolator. When the telco equipment closes the
loop and begins to send feed digits, the loop detect alerts the dual trunk card to receive the
inbound signaling (feed digits), which may be pulse, MF, or DTMF format. After feed digit
transmission is completed, the call enters page entry mode.
The call is terminated from the telco CO or PABX by opening the TIP/RING LOOP. The Model
640 reverses battery to disconnect the DID line.