HP 24SII - Manual (Page 72)

BETWEEN COMPUTER AND PERIPHERAL THROUGH MODEL
24SII
When a computer transmits data to a peripheral device through a
computer port on the Model 24SII DES, the data is received and
stored in the spooling buffer (standard 1MB; optional up to 16MB)
which in turn retransmits it to a peripheral device through a printer
port. During transmission, when the buffer fills, the Model 24SII DES
will send an XOFF, signaling the transmitting computer that it cannot
accept more data.
When the Model 24SII DES retransmits the data to the peripheral
device through a printer port, and the peripheral device cannot receive
any more data, the Model 24SII DES will expect to see a low on the
CTS (Clear-to-Send) line or receive an XOFF. When the peripheral
device can receive more data, the Model 24SII DES will expect to see
a high on the CTS line or receive an XON.
When the buffer of the Model 24SII DES can receive more data, the
Model 24SII DES will send an XON to the transmitting computer.
In the reverse direction (Peripheral-to-Model 24SII DES-to Computer),
handshaking is the same, but the spooling buffer is not utilized.
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 send an XOFF 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 or receive
an XON. When Computer B cannot receive any more data, the Model
24SII DES will expect to see a low on the CTS line or receive an
XOFF.