Samsung OFFICESERV 7100 Service Manual page 74

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QDMC provides 128 sub-time slots.
Digital Phone Interface
The AMI code is created from the QDASL(TP3404) and is transmitted to regular phones
through the Trans. The serial data are transferred to the QDMC by demodulating the AMI
code received from the phone through the Trans. The QDMC converts the entered serial data
to parallel data through the UART and transfers the data to the CPU. Also, /TSB of the
QDASL transfers the voice data of DASL to the highway.
Since one QDMC controls two QDASLs(a total of 8 ports), the /TSB signals generated
from each QDASL are added for use.
DLT-1 is used for a Trans for matching, and resistance of 100Ω in the QDASL LO adjusts
impedance. 2μF reduces noises. Two Zener diodes(3.6 V) in the Trans input part prevent hazard.
The power of -48V is supplied to the phone through the Poly switch to prevent over-current
from flowing to the phone. The varistor in the Trans input part prevents hazard.
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