G-9420
PAGE 4
January 2001
THEORY OF OPERATION
An incoming call to the G-9420 PALS
detects ringing voltage, U2, and signals
the main processor, U8. The PALS an-
swers immediately by going off-hook.
Relay K3 is energized, the front panel
LED, LE2, glows yellow and a 600 ohm
load is placed across the LINE IN to draw
loop current. The call-progress tone gen-
erator, U3, is controlled to send a double-
beep and indicate to the caller that a win-
dow of steering opportunity is available.
If a DTMF tone is sent, the DTMF decoder,
U5, instructs the processor of the tone
number sent and then closes the solid-
state switch, TS117, that corresponds to
that port and a second double-beep is ini-
tiated. At this point all the port LEDs ex-
tinguish except the port to be called and
the priority port if programmed. The pro-
cessor alternately places loop current and
ring voltage on the port using K4. The
red LED, LE3, will flash alternately with
the port LED (yellow) of the port ringing.
If the device on the port goes off-hook
during ringing, the ringing voltage col-
lapse detector, U9, will command the
ringing to cease immediately. If the de-
vice goes off-hook during non-ringing,
the TS117 will detect loop current flow
and the yellow port LED will go solid.
Once the port is determined by either case,
the processor connects the port to the line
by using K1 and then releases K3 to al-
low the port device to hold the line off-
hook. If multiple connections from one
call are enabled, when the port device
goes on-hook, the line is again placed off-
hook by the PALS before the line is lost to
no loop current being drawn. A double-
beep is again sent to allow the caller to
start the process over again, otherwise
the PALS hangs up the line.
If a port device wishes to call out, it must
go off-hook and draw loop current from
the local voltage source placed on all the
ports by K4 and K1. Since the port device
has drawn loop current, the PALS lights
its LED and the priority port LED if pro-
grammed. Also, the PALS connects the
port device to the LINE IN using K1 such
that the central office goes off-hook. The
TB1 K1
K3
K2 K4
U2
U9
U5
LE12
LE1
through
U3
U4
FIGURE 4
Simplified
layout
of the
G-9420
TP3
TP1
Line-In Ports
TP7
R11
R10
TP2
R46
J3
U8
18
the default value (*44010#).
DIAL TONE DISCONNECT
With the TLS and a handset con-
nected, connect a phone to port 1.
With the phone on port 1 on-hook,
momentarily depress the power but-
ton on the TLS to ON/RING. With
the Dial Tone Detection option en-
abled, the RING INDICATION LED
should illuminate and then go out.
Reprogram the G-9420 to disable
ring detection (*420#) and observe
that the G-9420 remains off-hook un-
til power-off. Reprogram back to en-
able dial tone detection (*421#).
BILLING DELAY OPTION
With the TLS and a handset con-
nected, dial a port of the G-9420. With
the billing delay enabled, a two-sec-
ond delay should be observed between
when the G-9420 goes off-hook and
when ringback tones occur in the TLS
handset. Reprogram the G-9420 to dis-
able the billing delay (*400#), and ob-
serve no delay. Reprogram back to the
default of enabled billing delay
(*401#).
RINGBACKS
With the TLS and a handset con-
nected, connect a phone to port 1.
With the TLS phone, call the G-9420
and count the number of rings before
the unit hangs up. This number
should match the default. Reprogram
the number of rings to 50 (*52150#)
and call the G-9420 and verify the
number of rings. Reset to the default
(*52116#).
PORT 1 CUT-THROUGH
With the TLS and a handset con-
nected, connect another phone to port
1. Power off the G-9420 and see that a
call will go through to port 1.
Phone Drive Tes
Attach 5 bell equivalent phones to a
port and ring that port. All phones
should ring!
FCC TESTS
Apply 1500 Vrms, 60 Hz from T to R of
the line in. This should not damage
the G-9420. Apply 1500 Vrms, 60 Hz
from T and R to the chassis, with no
damage to the G-9420. Apply 100
Vrms, 60 Hz to T&R and T&R to chas-
sis of all ports. No damage and no po-
tential present at the line in port or an-
other port should result.
Measure the line out noise level with
all phones on-hook. This should be
less than -60 dBm.
Measure the ring generator frequency.
Measure the ring generator frequency
while ringing a port with one phone
on it.
