SMS-758 Modem Protection Switch
Theory of Operation
MN/SMS758 Rev. 3
4–21
4.6.3.1 Electrical Specifications
V.35
Circuit Supported
SD, SCT, SCTE, RD, SCR, DSR, DSR, RLSD
Switching Format
Modulator and demodulator signals individually
with dry contacts
Contact Arrangement
Mod Signals:
8 poles
Demod Signals:
8 poles
Amplitude (RD, SCR, SCT, SD, SCTE)
0.55V peak
±
20
%
differential into 100
Ω
Amplitude (CTS, DSR, RLSD)
10
±
5V into 5000
±
2000
Ω
Impedance (RD, SCR, SCT)
100
±
20
Ω
Impedance (SD, SCTE)
100
±
10
Ω
Impedance (RTS)
5000
±
2000
Ω
,
<
2500 pF
DC Offset (RD, SCR, SCT)
±
0.6V max., 1000
Ω
termination to ground
Polarity (SD, SCT, SCTE, RD, SCR)
True when B positive wrt A
False when A positive wrt B
Polarity (RTS, SCT, DSR, RLSD)
True when
<
-3V wrt GND
False when
>
+3V wrt GND
Phasing (SCTE, SCR)
False-to-true transition, nominally in center of data
bit
Symmetry (SCR, SCTE, SCT)
50
%
,
±
5
%
Frequency
±
100 PPM
