IBM System/34 Maintenance Manual page 461

31-010 INTRODUCTION
Data communications is an optional feature that lets
System/34 function as a primary station (SOLe only) or
a terminal in a point-to-point or multipoint network.
Two communication features can be installed and run at
the same time. The hardware associated with line 1 is
described as line 1. The hardware associated with line 2
is described as line 2. Data is transmitted and received
serial-by-bit and serial-by-character over voice-grade
communication networks (switched or nonswitched), or
over DDSA. The system may be connected to a
half-duplex or duplex network but the adapter operates
in half-duplex mode only; that is, data transmission is
only in one direction at a time.
During transmit operations, each byte to be transmitted
is sent to the communications adapter where the data is
serialized and then sent one bit at a time to the modem
or digital adapter. The modem or digital adapter, then
sends the bits to the receiving terminal over the
communications network.
During receive operations, the communications adapter
receives each bit from the modem and assembles the
bits into bytes (deserializes). Each byte of data is then
sent to the processing unit.
31-100 LOCATIONS
Figures 31-1 and 31-2 show the locations of the major
parts used for data communications. The
communications adapter cards are always in location
A-A2J2 for line 1; and in location A-A2K2 for line 2.
The internal clock card, when used, is always in location
A-A2Q2 and supplies clock pulses for both line
1
and
line 2. The internal clock is used when the modem
does not supply an external clock.
Locations of other parts such as the integrated modems,
external adapters, and external cables are shown in
paragraphs 31-110 through 31-150.
2
31-010
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