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SYNCHRONOUS
OAT A SET (SDS)
BUFFER,
MODEL 70/721
GENERAL DESCRIPTION
COMMUNICATION
EQUIPMENT AND
FACILITIES
OPERA TlONAL
CHARACTERISTICS
70/721 Synchronous
Data Set Buffer
•
The RCA Model 70/721 Synchronous Data Set Buffer (SDSB) occupies one
scan position on the Communications Controller-Multichannel (CCM),
Model 70/668; and enables it to exchange control and bit-serial data signals
with EIA-standard synchronous data sets (i.e., those which provide a data
clock pulse). Operation is half-duplex, synchronous, at speeds of 2000 or
2400 bits per second. Two buffers and a special feature are required for
full-duplex operation. Optional capability is provided for using the fast-
turnaround provided by four-wire half-duplex circuits. A feature permits
automatic calling.
•
The buffer is compatible with the common-carrier communication
equipment and facilities indicated below or their equivalentso
Service
Grade
AT&T
Data
Notes
Data Set
Capacity
Private Line
Voice
201B
2400 bps
(1)
Message Network
Voice
201A3
2000 bps
(2)
Notes:
10 Four-wire, half-duplex operation permitted for fast-turnaround.
20 Automatic calling permitted via the AT&T 80lA or 80lC Automatic
Calling Unitso
• Control signals and data bits are exchanged between the SDSB and CCM
in a prescribed sequence:
1.
The CCM selects the buffer;
2. The buffer presents its status signals and data level;
3
0
The CCM issues command signals and a data level; and
4. The CCM drops Select, allowing the buffer to change its status
signals and data leveL
Note:
Signal and data levels are accepted by the buffer and CCM at strobe
time. The buffer drops the reports levels after receipt of RAK from the
CCM.
4-24
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