(1) Shutdown Feature. The jumpers which cause the power supply to shut down
upon removal of boards A3 or A4 are on EF and GH (fig. 1-7). These jumpers are
placed on AB and CD to override the shut down feature for troubleshooting.
However, they should be returned to EF and GH when the modem assembly is placed
back into normal operation.
(2) Transmit Output Level Switch. The transmitter output signal level is
controlled by a ten position screwdriver-adjustable switch located near board A7
O terminates the transmit
line in 600 ohms.
Transmit Output Level Switch
(3) Ground Jumper. A ground jumper (fig. 1-7) is provided to connect
pin 1 to signal ground pin 7 J1 thru J4) to signal ground (AB
J1). This ground jumper is factory set as shown in figure 1-7 (AC to DC
ground or Signal to Chassis Ground). The other terminal is used only when a ground
fault is suspected or when ground has an unsatisfactory noise level.