1-9. OPERATIONAL MODES AND CONTROLS. (CONT)
OUTGOING CALL WITH MODE SELECTOR SWITCH IN AC SUPV POSITION (CONT)
After the latch circuit stops the 2250 Hz seize tone, the switching facility stops sending the 570 Hz acknowledge signal. This energizes
the receive amplifier in the telephone set. The switching facility starts to send a dial tone signal (425 Hz). Once the dial tone is sent,
the following functions occur in the order given below:
The dial tone is received on the receive terminals of the telephone set and is sent to the receive amplifier where it is amplified and then
sent to the receiver element.
The calling party hears the dial tone, and presses the push button on the keysender for the first digit of the number he is dialing.
Pressing the push button energizes the dual tone multifrequency oscillator and tunes each oscillator (low and high group) for the
frequency of that digit.
The dual tone frequency is sent to the send amplifier which sends a signal to the switching facility. The switching facility acknowledges
the first digit dialed and stops the dial tone to the Telephone Set.
The calling party dials the rest of the numbers and the switching facility either processes the call or returns a busy signal. If a busy
signal is returned, it goes to the receive element of the calling party's telephone. If the called party is not busy, the call is connected
and a voice path is established.
When the call is completed, the handset is placed back in its cradle. At this time the hookswitch performs the following functions in the
order given below:
When the handset is placed in the cradle, the hookswitch contacts change the polarity of the input to the release timer circuit. This
energizes the release timer, the output of which goes to the release oscillator circuit and the send amplifier.
The oscillator is tuned to the 2600 Hz release frequency. The release signal is sent to the send amplifier.
The send amplifier sends the 2600 Hz signal to the switching facility. The switching facility acknowledges the 2600 Hz signal as a
signal for release and returns a 570 Hz acknowledge signal to the telephone set.
The release signal is received on the receive terminals which are coupled to the 570 Hz amplifier. Here the signal is amplified and