44023-1297 <90-00058>
P
AGE
7
The radio controls are switched on with Q9 (open collector). A
one-second delay network delays the radio control switch off.
The control timer provides a transmission delay of the drop and
line off-hook tones when you include radios or satellites in the
440 CMS. This delay turns on radios before you transmit the
tones.
The control timer provides two delay periods. The first delay
period (100 milliseconds) occurs at the end of a one-half second
charge period. The output of the inverter switches to a logic zero
(-10 VDC). Transistor Q12 switches on and starts the drop and
line off-hook tone burst timer (100 milliseconds) charge periods.
The on-hook tone burst timer also charges.
When Q12 switches on, relay K1 energizes. Contacts K1A close,
which:
♦
Connects a 200 ohm load across the two-wire tip and ring
inputs (through the A and B leads of a term set).
♦
Answers the call.
♦
Terminates the ring signal input to OC2.
When the ringing stops, the control timer tank circuit starts a
200 millisecond discharge delay period. At the end of the delay
period, the output of the control timer inverter switches to a
logic one (0 VDC). This causes the off-hook tone burst timers to
discharge, closing off-hook and alert-tone FETs and applying a
burst of tone to the LINE XMT and DROP RCV, respectively.
The off-hook LED also comes on.
The duration of the alert tone burst (proceed-to-dial signal) to
the drop is 0.12 seconds. This is to ensure that the system is
normalized before additional DTMF tones (address codes) are
sent. When the alert tone burst ceases, it indicates that the two-
or three-digit code for the desired 440 system station can be
dialed. The duration of the off-hook tone burst to the line is also
0.12 seconds. This is used to busy out the 440 system.
The no answer disconnect timer is also started when Q12 and
Q13 are turned on. If the incoming call is not answered within
the set time (10 to 80 seconds) the call is automatically discon-
nected. The timer activates an on-hook tone burst through the
line seize logic to unbusy the 440 system.
When the incoming call is answered at the 440 system remote
site, a ground is applied to the busy input (pin 22) from the
44021 Address Decoder in response to the off-hook tone. This
off-hook tone is generated at the remote site by a 49020 Tone
Supply Subassembly, activated through the remote 44022
Station Interface Module and applied to the 44021. The 44023
control circuit input (CCI) lead (pin 18) is grounded, either
permanently or through a switch.
The receipt of the busy input and CCI lead ground puts the
44023 under the control of the 440 system site and disables the
no answer disconnect timer. This allows the call to proceed
indefinitely or until the 440 system site goes on hook.
CIRCUIT DESCRIPTION
