The suspend message indicates a temporary cessation of communication without releasing the call. It can only be accepted during the conversation/data phase.
A suspend message can be generated by the network in response to a clearback indication from an interworking node or an on-hook condition from an analogue called party.
a) Action at the destination exchange or an interworking exchange
On receipt of an on-hook condition in the destination exchange or a clearback signal at the interworking exchange, the exchange may send a suspend (network) message to the preceding exchange.
b) Action at the intermediate exchange
On receipt of a suspend message the exchange will send a suspend message to the preceding exchange.
c) Action at the controlling exchange (i.e. exchange controlling the call)
On receipt of the on-hook condition or clearback indication or suspend message, the controlling exchange starts a timer (T6) to ensure that an off-hook condition, a re-answer indication, a resume (network) message or a release message is received and, if applicable, sends a suspend (network) message to the preceding exchange. The value of this timer (T6) is covered in Recommendation Q.118 [10]. If the timer (T6) expires, the procedures in 2.4.3 apply.
d) Actions at the incoming international exchange
On receipt of the on-hook condition or clearback indication or suspend (network) message, the incoming international exchange sends to the preceding exchange a suspend (network) message and starts a timer (T38), to ensure that a release message is received. The value of this timer is covered in Recommendation Q.118 [10]. If the timer (T38) expires, the procedure in 2.4.3 applies. The procedure described above may not be applied in the incoming international exchange if a similar arrangement is already made in the network of the incoming country.
A resume message indicates a request to recommence communication. A request to release the call received from the calling party will override the suspend/resume sequence and the procedures given in 2.3 will be followed.
A resume message is initiated by the network, if a suspend message had previously been sent, in response to a re-answer indication from an interworking node or an off-hook condition from an analogue called party.
a) Action at the destination exchange or interworking exchange
On receipt of a re-answer indication at the interworking exchange or an off-hook condition in the destination exchange, the exchange may send a resume (network) message to the preceding exchange if a suspend (network) message had previously been sent.
b) Actions of the intermediate exchange
On receipt of a resume message the exchange will send a resume message to the preceding exchange.
c) Action of the controlling exchange (i.e. exchange controlling the call)
On receipt of the off-hook condition, re-answer signal, or resume (network) message the controlling exchange stops the timer (T6) [started in 2.4.1 c)] and, if applicable, sends a resume (network) message to the preceding exchange. On receipt of a release message the controlling exchange stops the timer T6 and releases the call according to the procedure in 2.3.
d) Actions at the incoming international exchange
On receipt of the off-hook condition, re-answer signal, or resume (network) message from the succeeding exchange, the incoming international exchange stops the timer (T38) [started in 2.4.1 d)] and sends a resume (network) message to the preceding exchange. On receipt of a release message the incoming international exchange stops the timer T38 and releases the call according to the procedure in 2.3.
If a request for reconnection or a resume (network) message is not received within timer (T6) or timer (T38), both covered in Recommendation Q.118 [10], then the exchange where the timer has been started will initiate the release procedure on both sides. Cause value #16 (normal call clearing) is used in the release message on expiry of T6; cause value #102 (recovery on timer expiry) is used in the release message on expiry of T38.