HP 24SII - Manual (Page 71)

BETWEEN COMPUTER AND COMPUTER THROUGH MODEL
24SII
When Computer A transmits data to Computer B through the Model
24SII DES, the data is received from Computer A and stored in a
512-character buffer which in turn retransmits it to Computer B. When
the buffer fills, the Model 24SII DES will make the DTR line low to
Computer A, signaling Computer A that it cannot accept more data.
When the Model 24SII DES retransmits the data to Computer B, the
Model 24SII DES will expect to see a high on the CTS line. When
Computer B cannot receive any more data, the Model 24SII DES will
expect to see a low on the CTS line.
When the buffer of the Model 24SII DES can receive more data, the
Model 24SII DES will make the DTR line high to Computer A.
+!+
NOTE: The Model 24SII DES permits XON/XOFF to be enabled or
disabled by port independently in the receive and transmit directions.
The description of handshaking functions below considers XON/XOFF
to be enabled in both directions. If XON/XOFF is disabled in one
direction, that direction will support hardware handshaking as
described in
Section 7.3.1 .