Specifications

AN93
126 Rev. 0.8
DC Termination
The ISOmodem offers a great deal of flexibility in setting
dc termination. Several bits can be used to adapt to
particular country requirements and unusual line
conditions. The dc termination control bits are shown in
Table 96.
A detailed description of each bit is given in the relevant
U-Register description section of this manual. The
following discussion centers on the use of these bits
alone or in combination to meet particular country
requirements.
Yugoslavia – Special Network Require-
ments
The following are special network requirements for
Yugoslavia. These specifications are based on the best
information available and are believed to be correct. A
complete specification was not available.
 DC Feed: 48 or 60 V
 Feeding Bridge: 2x400 Ω or 2x500 Ω
 Network Impedance: 600 Ω resistive
 On-Hook (Idle State) Noise: <–60 dBm
 On-Hook ac (Ringer) impedance: >2.5 kΩ
 DTMF Transmit: –9/–11 dBm and –6/–8 dBm are
allowed.
 Data Transmit Level: 0 dBm to –15 dBm in 1 dB
steps (average –13 dBmo)
 Out-of-band energy: Not specified
 Pulse Dial: 1.6/1 ±15% (Pulse/pause)
 Rep Rate: 10 pps
 Interdial Pause: 250 ms <x> 800 ms, ±10%
 Ring Tone: 25 Hz 80–90 V
eff

Dial Tone: 425 Hz ±15%
 Level: –8 dBm > x > –12 dBm
 Cadence: 200 ms ±10% ON
300 ms ±10% OFF
700 ms ±10% ON
800 ms ±10% OFF
 Busy Tone: 425 Hz ±15%
 Level: –8 dBm > x > –12 dBm
 Cadence: 500 ms ±10% ON
500 ms ±10% OFF
Table 94. Dial Registers
Register Value Function
Pulse Dial Control
U37–U40 Pulse per Digit Definition
U42 PDBT Pulse Dial Break Time
U43 PDMT Pulse Dial Make Time
U45 PDIT Pulse Dial Interdigit Time
DTMF Control
U46 DTPL DTMF Power Level (and
Twist)
U47 DTNT DTMF On Time
U48 DTFT DTMF Off Time
Table 95. Line Interface/Control Registers
Register Bit Value Function
U4D 10 CLPD Check Loop Current Before
Dialing
1 LLC Low Loop Current Detect
(set for CTR21)
0 LCN Loop Current Needed
U50 LCDN Loop Current Debounce On
Time
U51 LCDF Loop Current Debounce Off
Time
U52 XMTL Transmit Level
U67:
13:12
MINI
9 ILIM
7 DCR DC Impedance Select
6 OHS On-Hook Speed
3:2 DCV DC Termination Select
1 RZ Ringer Impedance
0 RT Ringer Threshold Select
U68 2 BTE Billing Tone Protect Enable
1 ROV Receive Overload
0 BTD Billing Tone Detected
Table 96. DC Termination Control Bits
Reg Bit Val Function
U67 7 DCR DC Impedance Select
U67 3:2 DCV DC Termination Select
U7D 10 LLV Special low-voltage mode
Table 96. DC Termination Control Bits