User guide

ASCOM USER GUIDE
High Speed Base Band Modems
55
8.3.2 Module Link Settings
J1 – V35 Circuit 113 (External Signal Element Timing) Input Polarity Selection – This aspect of
the V35 interface may be implemented differently by different manufacturers. This link allows
the authorised personnel to swap the polarity of the A and B wires of this differential input
circuit. The factory default setting for this position 1-2.
8.3.3 External Timing
If External timing is required i.e. the modem is to be used as a DTE then a change over cable
will be required as shown in the diagram below.
P 103-A P 103-A
S 103-B S 103-B
R 104-A R 104-A
T 104-B T 104-B
C 105 C 105
F 109 F 109
U 113-A V 115-A
W 113-B W 115-B
B GND B GND
Master
High Speed
Modem
Set to
External
Bit Timing
Timing
Source
2
2
J1A
Interface Module -
Top View
3
3
J1B
MRAC Connector
8
54 ASCOM USER GUIDE
High Speed Base Band Modems
The circuit 105 - circuit 109 crossover may not be necessary if circuit 105 is clamped to the on
position (section 6.4.2.2).
Additionally, if circuits 108 and 107 are used in the handshaking procedure, they may be
crossed as well.
8.3 V.35
8.3.1 V.35 (MRAC) Connector Pin Allocation
Note: that on some MRAC connectors pin `AA’ is marked as `a’ and pin `NN’ is marked `m’.
Pin Type SITS
Unbal A-wire B-wire Circuit Description 89/43
B 102 Common Return Common
P S 103 Transmitted Data Load
R T 104 Received Data Generator
C 105 Request to Send Load
D 106 Ready for Sending Generator
E 107 Data Set Ready Generator
F 109 Data Channel Received Generator
U W 113 External Transmitter Signal Element Timing Load
Y AA* 114 Transmitter Signal Element Timing Generator
V X 115 Receiver Signal Element Timing Generator
N 140 Remote Loopback Load
L 141 Local Loopback Load
NN* 142 Test Indicator Generator