Casio UP-250 Technical Manual page 145

If the electric potential of CS1 is higher than CS2, the TM series printer is ready for
communication (the host is ready to receive data). If the electric potential of CS1 is lower than
CS2, the TM series printer is not ready for communication (the host is not ready to receive data).
DR1 DR2
H L
L H
If the electric potential of DR1 is higher than DR2, the TM series printer is ready for
communication (the host is ready to receive data). If the electric potential of DR1 is lower than
DR2, the TM series printer is not ready for communication (the host is not ready to receive data).
Communication is available
Communication is not available
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Function
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