Dataman S4 - Manual (Page 81)

DATAMAN S4 MANUAL
RS232 Serial Interface 81
RS232 Serial Interface
The serial RS232 interface uses an IC made
by Motorola, part number MC145406, which
meets RS232 standards of voltage and current
on inputs and outputs.
Current can be sourced by the outputs into
any load on the RS232 interface, but it is
unlikely that such current will exceed 5ma.
Nevertheless this current comes from the
battery. Leaving the RS232 lead connected
will reduce battery life by about 20%. When
S4 powers down, the RS232 voltages fall to
zero.