[RTTY] USOS Question

[Phil Sussman]

Not to beat a dead horse and I'm sure that I've asked this question before.
I just can not find the related answer.

While I understand USOS, I can't differentiate between sending and receiving
USOS. In other words is USOS employed only by those transmitting, only by those
receiving, -or- in combination?

It is simplistic, such as:

Sending Station              Receiving Station

USOS off                     USOS off
USOS off                     USOS on
USOS on                      USOS off
USOS on                      USOS on

Or does it lead to these sixteen possibilities:
 
Sending Station              Receiving Station

USOS TX off  USOS RX off     USOS TX off USOS RX off
USOS TX off  USOS RX off     USOS TX off USOS RX on
USOS TX off  USOS RX off     USOS TX on  USOS RX off
USOS TX off  USOS RX off     USOS TX on  USOS RX on

USOS TX off  USOS RX on      USOS TX off USOS RX off
USOS TX off  USOS RX on      USOS TX off USOS RX on
USOS TX off  USOS RX on      USOS TX on  USOS RX off
USOS TX off  USOS RX off     USOS TX on  USOS RX on

USOS TX on   USOS RX off     USOS TX off USOS RX off
USOS TX on   USOS RX off     USOS TX off USOS RX on
USOS TX on   USOS RX off     USOS TX on  USOS RX off
USOS TX on   USOS RX off     USOS TX on  USOS RX on

USOS TX on   USOS RX on      USOS TX off USOS RX off
USOS TX on   USOS RX on      USOS TX off USOS RX on
USOS TX on   USOS RX on      USOS TX on  USOS RX off
USOS TX on   USOS RX on      USOS TX on  USOS RX on

Yeah, I'm confused.

Can you set me straight, Chen (or anyone else)?

Thanks,

de Phil - N8PS