Outgoing sender
An Outgoing Sender (out-sender or OS) is a circuit in some electromechanical telephone switches that is responsible for sending information forward to another telephone switch.[1] Outgoing senders can accomplish this using a variety of signaling methods, depending on the needs of the exchange.
Outgoing senders are distinct from other types in that they are exclusively used for sending information forward. This is in contrast to other types of senders such as terminating senders or subscriber senders, both of which also receive information.
The capabilities of an outgoing sender are determined by its circuit design. Usually, an outgoing sender transmits using only one or two protocols, as this makes the sender less cumbersome to design and implement. In order to support all necessary signaling types, a telephone switch might employ several different types of out-senders.