TELEPHONE INTERFACE MODULE (TIM)

14.10 E&M SETUP AND ALIGNMENT (-680)

The standard audio signal is defined as a 1 kHz audio tone modulated at 2 kHz deviation, with data modulated at 1 kHz deviation (total deviation is

3 kHz).

Table 14-7 E&M MAIN BOARD JUMPERS

 

JU

Pin

Description

 

 

 

 

 

 

 

J24

1 to 2*

Selects 27512 EPROM operation

 

 

 

2 to 3

Selects 27256 EPROM operation

 

 

J27

1 to 2

Not used

 

 

 

2 to 3*

Normal operation

 

 

P33

1 to 2

open

 

 

 

3 to 4

open

 

 

 

5 and 6

open

 

 

J36

2 to 3

For E&M operation

 

 

J14

Jumper pin 1 to 2 for high impedance ground path

 

 

J15

for split 600 ohm inputs and outputs. Leave open if

 

 

J21

no ground path desired.

 

 

J22

 

 

 

 

* Indicates normal operation.

 

 

Table 14-8 E&M JUMPER PLACEMENT

 

 

 

 

 

 

 

JU

Pin

Description

 

 

 

 

 

 

 

J207

1 to 2

Connects Dial Tone circuit

 

 

 

2 to 3

Removes Dial Tone circuit

 

 

J209

1 to 2

Connects SG to Switch 0V (gnd)

 

14.10.1 EQUIPMENT REQUIRED

1.Digital storage scope (Tektronix 2430 or equivalent with roll mode trigger capability from 100 ms to 1 second).

2.Printer or plotter for scope (recommended for sending data back to E.F. Johnson for analysis).

3.Telephone test set (Ameritec V.F. test set model AM-44 or equivalent).

4.RF communications monitor.

5.Multi-Net Encoder/Decoder Box.

14.10.2 TRANSMIT ALIGNMENT

DTMF Transmit Level Adjust

1.Set S5 on the main board for Test 3 (sections 1 and 2 open, 3 and 4 closed).

2.Adjust R214 for -7 dB at TP201 (EP201). This sets the correct level of TX DTMF with respect to TX Audio.

NOTE: After adjusting this level, DTMF and audio are adjusted together by R44 (TX+/TX-). TX+ DTMF and audio are monitored at J12.

Transmit Audio Level Adjust

This procedure requires a fully tuned repeater for testing. Test this repeater by keying up in dispatch mode with a radio. Monitor the receive frequency and record the receive data level. Generate a DTMF 5 from the radio and record the total deviation of data + audio. Subtract the previous data level and record the audio level received.

Monitor the transmit frequency of the repeater. Key up the radio and record the transmit data level. Generate a DTMF 5 from the radio and record the total deviation of data + audio. Subtract the data level previously recorded and record the audio level received. This level of audio should be the same as the receive level. If not, retune the repeater before proceeding with this procedure.

Disable dial-tone detection in the Call Processor. With a known good repeater, attempt to make a call to a test phone over the 4-Wire circuit. If the call did not go through, check digit timing parameters (pulse and DTMF) or the level of DTMF transmitted at TX+/TX-

. Normally this level is -7 dBm (346 mV RMS or

978 mV P-P). If the 4-Wire requires a different level adjust R44 while monitoring the transmit level for the appropriate level.

Once the call is connected to a test phone (a phone located at the site provided the call went through the CO or PBX), collect the repeater using the Multi-Net Encoder/Decoder box and communications monitor with a data level of 1 kHz. With the call still going, turn off the radio (do not pound '#' down the

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