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E-4 LEAD DEFINITIONS
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Table E-3. EIA RS-449 (V.24) LEADS/DEFINITIONS
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PIN EIA LEAD DESCRIPTION MPDM (Note)
NO. INTERCHANGE CIRCUIT (FUNCTION) INPUT/OUTPUT
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1 — Shield —
2 SI Signal Rate Indicator I
3 — Unassigned —
4 SD(A) Send Data I
5 ST(A) Send Timing O
6 RD(A) Receive Data O
7 RS(A) Request to Send I
8 RI(A) Receive Timing O
9 CS(A) Clear to Send O
10 LL Local Loopback I
11 DM(A) Data Mode O
12 TR(A) Terminal Ready I
13 RR(A) Receiver Ready O
14 RL Remote Loopback I
15 IC Incoming Call O
16 SR Signaling Rate Selector I
17 TT(A) Terminal Timing I
18 TM Test Mode O
19 SG Signal Ground X
20 RC Receive Common O
21 — Unassigned —
22 SD(B) (Note) Send Data I
23 ST(B) (Note) Send Timing O
24 RD(B) (Note) Receive Data O
25 RS(B) (Note) Request to Send I
26 RT(B) (Note) Receive Timing O
27 CS(B) (Note) Clear to Send O
28 — Unassigned —
29 DM(B) (Note) Data Mode O
30 TR(B) (Note) Terminal Ready I
31 RR(B) (Note) Receiver Ready O
32 — Unassigned —
33 SQ Dummy Generator ON O
34 — Unassigned —
35 TT(B) (Note) Terminal Timing I
36 SB Dummy Generator OFF O
37 SC Send Common I
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Note: Denotes category II or balanced circuits. All MPDM interchange circuits are implemented with RS-
423 line drivers.