Dropout Delay And Ptt; And Q7); Reverse Key-Up; Reverse Audio Path - Motorola CDR500 Programming Manual

Basic Repeater Controller
Theory of Operation
TX and J4-ACC. S2-6 will route the audio to the micro-
phone transmitter audio, pin 3 of J2-TX and pins 2 of
J3-TX and J4-ACC.
R23 is used to adjust the receive radio audio output to
the proper level for the transmit radio audio input. The
audio gate is enabled with an active dc level low at
either pin 8 or pin 14 of J5-RX. The gate can also be
hard enabled if S2-7 is closed.
Dropout Delay and PTT (Q5, Q10, U1B

and Q7):

The dropout delay circuit uses the second half of U1, the
MC14013B dual D flip flop, to generate a PTT signal for
the transmit radio. The Q output, pin 13, of U1B is low if
the repeater is inactive. When an input signal is present
at the receive radio, either pin 8 or pin 14 of J5-RX will
be pulled low and turn off Q15. Q5 will turn on and dis-
charge C3. Q10 will turn on when the voltage across C3
is less than 4.5 Vdc. The output from Q10 pulls the PRE-
SET input of U1B high. The Q output of U1B switches to
a high state and turns on Q7. Pin 4 of J2-TX and pin 3 of
J3-TX are pulled low and key the transmit radio PTT.
The red COR LED, CR2, illuminates.
The dropout delay is generated when Q5 ceases to con-
duct. Q10 will remain on until the voltage across C3
reaches 4.5 Vdc or greater. S2-10 and S2-11 are used to
switch in the appropriate resistance to generate the
desired time constant.
S1 on the front panel is used to enable the repeater
function and will not allow Q7 to conduct unless it is in
the enable (in) position. S1 also interrupts the COR sig-
nal from pin 8 or pin 14 of J5-RX and the output of the
VOX circuit to disable the repeater.

Reverse Key-up

Whenever pin 8 of J3-TX goes low, it will pull pin 3 of J5-
RX low. When the reverse key-up function is being used,
as in the bi-directional repeater configuration, S2-3 must
be open and no functions can be programmed which will
use pin 8 of J5-RX. A NULL with active LOW state on pin
8 will prevent any unwanted reverse key-up.

Reverse Audio Path

Audio present on pin 11 of J3-TX is routed to either pin
2 or pin 5 of J5-RX. S2-8 and S2-9 determine to which
pin the audio is routed. As with the forward direction,
a potentiometer, R24, is used to adjust the audio level.

Accessory Jack (J4-ACC)

The accessory jack, J4-ACC, is connected to J3-TX and
J5-RX such that all of the Radius standard accessories
will still be compatible. Furthermore, the standard con-
nections are retained (no new cables need to be made).
The only input which causes the Basic Repeater Con-
6-2
troller to respond is pin 3 of J4-ACC (PTT). A low on
the pin will cause a low on pin 3 of J3-TX and keying
of the transmit radio.

DIP Switch (S2) Functions

DIP Switch positions for the Basic Repeater Controller
(* = typical setup):

S2-1

S2-1 routes the PL/DPL & CSQ I/O signal (active low)
from J3 pin 8 of the transmit radio to J3 pin 3 (the PTT)
of the receive radio in the bidirectional repeater config-
urations. For unidirectional repeaters, S2-1 should be
OFF.
S2-1 should be set:
• OFF* for unidirectional repeaters
• ON for bidirectional repeaters.

S2-2 and S2-3

S2-2 selects pin 14 of J5-RX as the COR input from the
receive radio; S2-3 selects pin 8 of J5-RX for the same
function. Either S2-2 or S2-3 should be ON with the
other switch in the OFF position. However, no harm to
the Basic Repeater Controller or the receive radio
occurs if both of the switches are accidentally ON. In
the bidirectional repeater configuration, continuous
keying of the transmitter of the receive radio occurs if
S2-3 is ON, therefore S2-2 (pin 14 I/O) must be used.
S2-2 should be set:
• OFF* for pin 8 I/O (CSQ or TPL/DPL)
• ON for pin 14 I/O (CSQ or TPL/DPL).
S2-3 should be set:
• OFF for pin 14 I/O (CSQ or TPL/DPL)
• ON* for pin 8 I/O (CSQ or TPL/DPL).

S2-4

S2-4 enables the remote Setup/Knockdown feature
which requires the MDC-1200 RapidCall signalling
format with a CDM1250, CDM1550, PRO5100, or
PRO7100 mobile radio for the receive radio. The Basic
Repeater Controller supplies operating voltage to J3
pin 10 (the ignition control input) of the transmit radio.
S2-4 should be set:
• OFF* for local only repeater Setup/Knockdown
• ON to enable remote Setup/Knockdown
(MDC-1200).

S2-5 and S2-6

S2-5 and S2-6 are used to select the routing of the audio
from the receiver of the receive radio to the proper audio
6864110R66-O
CDR500 & CDR700 Repeater Service Manual
March, 2001