Teletype SA120 Description And Operation

BELL SYSTEM PRACTICES
AT&TCo Standard
SECTION 578-200-101
Issue 1, September 1971
PARITY FAILURE DETECTOR AND
SUBSTITUTE CHARACTER INSERTER (SA120)
DESCRIPTION AND PRINCIPLES OF OPERATION
CONTENTS
PAGE
1. GENERAL ................. . 1
PHYSICAL CHARACTERISTICS . . . . 4
ELECTRICAL CHARACTERISTICS ..
5
A. Input . . . . . . . . . . . . . . . . . . . 5
B. Output . . . . . . . . . . . . . . . . . . 5
2. DESCRIPTION... . . . . . . . . . . . . . 5
ASSOCIATED EQUIPMENT
WIRING DIAGRAMS . . . . . . . . . . . . 5
RECEIVING LOGIC . . . . . . . . . . . . 6
SENDING LOGIC . . . . . . . . . . . . . . 9
3. PRINCIPLES OF OPERATION . . . . . 10
GENERAL . . . . . . . . . . . . . . . . . . 10
OPERATING SEQUENCE. . . . . . . . . 10
POWER SUPPLY.............. 15
4. VARIABLE FEATURES . . . . . . . . . 17
OPERABLE COMBINATIONS AND
CODE ASSIGNMENTS . . . . . • . . . . . 17
OPERA TING SPEEDS AND
BIT TIMERS. • . . . . . . . . . . . . . . . 17
PARITY INSERT CIRCUIT CARD . . . 21
A. Description. . . . . . . . . . . . . . .
21
B. Principles of Operation. . . . • . . 21
INTERFACE CIRCUIT CARD FOR
CURRENT /NO CURRENT DATA
SETS (lOlC OR 105A) AND 33 OR 35
TERMINALS • . . . . . . . . . . . . . . . . 23
A. Description. . . . . . . . . . . . . . . 23
B. Principles of Operation. . . . . . . 24
CONTENTS PAGE
BREAK GENERATOR/COUNTER
DRIVER CIRCUIT CARD . . . . . . . . . 24
A. General . . . . . . . . . . . • . • . • . 24
B. Description. . . . . . . . . . . . . . . 25
C. Principles of Operation. . • . . . • 28
BYPASS SWITCH AND INDICATOR
ASSEMBLIES . . . . . . • . . . . . . . . . 31
A. General . . . . . . • . . . . . . . . . . 31
B. Bypass Switch and Indicator
Assemblies for 33 Type Sets 31
C. Bypass Switch and Indicator
Assemblies for 35 Type Sets 35
D. Bypass Switch and Indicator
Assemblies for Type 2 Tape
Senders and Receivers . . . . . . . 35
1. GENERAL
1. 01 This section provides the description and
principles of operation for the SA120
parity failure detector and substitute character
inserter (Figure 1). It also provides the associ-
ated bypass and indicator assemblies (Figure 2).
Refer to Section 578-200-201 for installation
information, Section 578-200-301 for check-
out and troubleshooting procedures, Section
578-200-801 for parts, and to WDP0204 for
complete wiring diagram package.
1. 02 As a parity detector, substitute character
inserter and regenerative repeater for a
receiver, the SA120 may be applied to Model 33
and 35 type automatic send-receive or receive-
only terminals or to Type 2 Tape-To-Tape
Systems. As a parity inserter and/or regener-
ative repeater, one SA120 version may be used
with a sender. The SAl 20 parity detector can
be
used with any eight-level serial-by-bit signal
that provides a parity bit, at any speed up to
2400 wpm.
Prepared for American Telephone and Telegraph Company by Teletype Corporation
© 1970 by Teletype Corporation
All rights reserved
Printed in U. S. A. Page 1