ZETRON 4010, Руководство по обслуживанию

Страница: 12 / 123

Model 4010 Radio Dispatch Console Service Manual
12
digital communication to the board. The two channels function similar and only channel A will be
followed. The data in from the microprocessor (DI) are synchronously clocked to the 16 bit serial
shift register U26 and U29 using the CHWR* and ENCHA* signals. The data to the microprocessor
(DO) is simultaneously clocked out of U35. U26 and U29 form a 16-bit output latch, which controls
the operation of the board. The outputs are buffered by U18 and U23, which convert the 5V signals
to 12V to drive the various audio switches. U35 is an 8-bit input port that specifies the board type
and monitors the ring detector and call activity.
The telephone line’s tip and ring are connected to J1. In the off-hook state, the signal goes through
relay K1 to the ring detect circuit of U19. The signal flows through U22C, U22F and U28A to U35.
The microprocessor reads the status of U35 with the SPI bus. The ring detect signal also goes
through U18A to the tone generator U6. When a ring is detected, U6 generates a ringing tone at pin
14 and sums it on the audio receive bus at U3A. When the call is answered, relay K1 is activated
with the AUXOUTA signal and the line is switched to relay T1.
The three input audio busses are PAT-TX-BUS (patch transmit bus), TONE-BUS (DTMF tones) and
MIC-BUS (operator’s audio). These busses are switched by U17A and U17B to the input of U8B.
The output of U8B goes to the audio switch U15C is used to enable the audio to the output amplifier
U4A. The audio also goes to U11, which forms a peak detector that prohibits the transmitted audio
from exceeding -10dBm average for over 2 seconds. The output of the detector controls the audio
switch U15C through U18C.
The center tap of the transformer T1 is connected to the line termination network of U1A. Potentio-
meter R16 set the resistive balance and is usually set for minimum sidetone. R21 is used for capaci-
tive balance and is also adjusted for minimum sidetone. The audio receive amplifier, U1B, goes
through the switch U15B and to the audio level adjustment R18. U3B form a peak detect circuit and
generates the voice activated signal to U35. The receive audio also goes to the summing node of
U3A. The audio signal goes to the switch U15A to the PATCH-RX-BUS and to U13, the volume
control selector. U13 multiplexes the RXA signal through a resistive network to give 4dB adjustment
steps. The A, B and C signals to U13 selects which resistive path the audio takes and the INH signal
will inhibit all switches from closing and provide a completed muted signal. If no audio muting is
selected, the audio will be switched through R72 giving the maximum signal level. The output
amplifier U8A will drive either the SEL-BUS or UNS_BUS depending on the U17C switch setting.
AUXILIARY I/O CARD (950-9721)
The Auxiliary I/O Card will expand the I/O capability of the system by adding 6 outputs and 6
inputs. The card is installed in any of the six dual channel card slots and the connection to the I/O are
on the interface connectors J2 through J4 depending on the slot(s) the card is installed in.
The I/O Card schematic 008-9448 shows the SPI bus signals DI, DO, SCLK* and enable signal
ENCHA*. The data in from the microprocessor (DI) are synchronously clocked to the 8-bit serial
shift register U2 and into the output latch using the CHWR* and ENCHA* signals. Six of the out-
puts use the transistor driver IC, U1, to control the output relays K1 through K6. The data to the
microprocessor (DO) is simultaneously clocked out of U5 and U6. U5 monitors the six input signals
and U6 identifies which card type is installed.
The inputs from the interface connector have a 10K-ohm pull-up to 12Vdc, a 10K-ohm series
resistor, a Zener diode to limit the voltage level and a .01 microfarad capacitor for noise filtering. U4
is a 74HC14 that provides a Schmitt trigger input.
The relay outputs each have two jumpers associated with them. Output 1 has one connection RLY1A
on P4-5 and the second connection RLY1B on P4-4. The RLY1A connects to JP7, which makes a
normally open output in position A and a normally closed output in position B. The common connec-
tion of K4 goes to JP1, which is connected to RLY1B in position A. With JP1 in position B the relay
common is connected to digital ground. With jumpers in both positions B and D the RLY1A signal
is connected to ground when the output is on and RLY1B is connected to ground when the output is
off.
TONE REMOTE SYSTEM ADAPTER (950-0255)
The Tone Remote System Adapter adds the tone remote capability to all the radio channels. The card
adds the 2175Hz guard tone to the system and guard tone filters on the four audio busses. The
schematic for the card is 008-0037.
From the Control Board’s interface connector J1, the unselect bus (UNS IN), select bus (SEL IN),
microphone bus (MIC IN) and the patch bus (PAT IN) all go through a low-pass filter to a 2175HZ
notch filter. The switch capacitor filter (U19 through U22) is a 35dB notch filter centered at 2175Hz
and a 200Hz bandwidth. The output of the notch filter, N/HPB, goes trough a low-pass filter and
back to the interface connector J1. The jumpers JP6 and JP7 allow the filters to be removed for the
patch bus and mic bus.
U17 interface to the crystal Y1 and along with U14 and U16B form the 2175Hz oscillator. U18B and
U15 form a filter and amplifier for the guard tone. R47 provides the amplitude adjustment.
Sheet 2 of the schematic is for audio delay, and the components are not included with this assembly.
TONE REMOTE SYSTEM ADAPTER W/AUDIO DELAY (950-9922)
The Tone Remote System Adapter with Audio Delay adds the tone remote capability to all the radio
channels. The card adds the 2175Hz guard tone to the system and guard tone filters on the four audio
busses. The card also provides a variable audio delay for two of the busses, patch bus and
microphone bus. The schematic for the card is 008-9896.
From the Control Board’s interface connector J1, the unselect bus (UNS IN), select bus (SEL IN),
microphone bus (MIC IN) and the patch bus (PAT IN) all go through a low-pass filter to a 2175HZ
notch filter. The switch capacitor filter (U19 through U22) is a 35dB notch filter centered at 2175Hz
and a 200Hz bandwidth. The output of the notch filter goes through a low-pass filter. The select bus
and unselect buses are then the UNS OUT and SEL OUT signals on connector J1. The patch bus and
mic bus go to the jumpers JP6 and JP7 which allow the notch filters to be bypassed and then go to
the audio delay circuits on sheet 2.