Specifications

T400 Controller Facilities Manual
667/EB/20200/000 Page 25-14 Issue 9
25.2.7 Effect of Incorrect Switch Settings on the Ancillary Processor PCB
(i) S1 - 2/4 Wire Select Switch
4 wire system but with 2 wire selected in error or 2 wire system but
with 4 wire selected in error; the OTU may not receive the control
signal and will not reply, therefore the carrier detect and transmit
confirm LED’s will be OFF.
(ii) S2 - Lithium Battery On/Off Switch
If this switch is off the system fail LED will illuminate on the T400
Main Processor PCB and the Integral OTU will not communicate with
the Instation.
(iii) S3 - Line level switch
A 6-way DIL switch is used to set line levels. If switch positions 1 to 4,
of the DIL switch, are set incorrectly the OTU will transmit at the
wrong output power.
If switch positions 5 and 6 are set incorrectly the receive threshold for
the OTU modem will be wrong. If it is set too low corrupted control
messages may occur. If set too high the control messages from the
Instation may be undetected.
(iv) S4 - 600 Ohm/High Impedance Switch
If the switch is set to high impedance when it should be set to 600
Ohms, the transmit signal for all OTU’s on the line and the receive
signal for the particular OTU will be up to 3dB higher than if the switch
was set correctly. The characteristics of the line may also be affected.
If the switch is set to 600 Ohms when it should be set to high
impedance this will reduce signal levels and may upset the
characteristics of the line.