XEISDNP 查看數據表（PDF） - Xecom
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XEISDNP Datasheet PDF : 8 Pages
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Central Office Function
The XEISDNP Analog Phone Line Adapter provides an interface between an ISDN Terminal
Adapter data channel and an analog (POTS) telephone. In an analog (Plain Old Telephone Service)
system the Central Office (CO) of the telephone company supplies a customer telephone with DC
power when the subscriber handset is removed from the hook (off-hook) and delivers calling progress
tones, like Dial tone, Ring-back signal and Busy signal when the phone is in use. In addition, when a
call arrives while the handset is on-hook, the CO sends an AC signal to ring the phone set. The CO
detects and digitizes the key tones or dial pulses and the subscriber’s voice signals for transmission
through the network.
ISDN provides a pure digital service to the subscriber, with no provision for line power or analog
signaling tones. Therefore to use analog equipment with ISDN service these functions must be
provided locally. The XEISDNP is designed to duplicate the analog user front end (line card) of a
Central Office switch. The following list summarizes the CO functions which the Adapter must replace:
• Sending ring signal to an on-hook phone when its number is called.
• Sending supply power to the telephone set when it is off-hook.
• Sending calling progress tones, including dial tone, busy signal and ring-back tone.
• Detecting and encoding the tones generated when the user “dials” a number.
• Coding the local users voice signal for the digital system and decoding the incoming digitized voice
data to an analog signal for the local hand-set.
Adapter Functional Blocks
CODEC
The CODEC inside the XEISDNP converts the voice signal from the telephone handset to a digital
data stream and sends it to the ISDN Terminal Adapter. From the other direction it receives the
processed B channel bit stream from the Terminal Adapter, converts it to analog voice signal, then
sends it to the telephone handset. The coding/decoding scheme may be changed from A-law to Mu-
law by switching the pin 27 Mu/A setting. The communication between the CODEC and the ISDN
controller uses either GCI( also known as IOM-2) or IDL standard depending on the logic level of pin
46. The data channel can be set for B1 or B2 of the ISDN line by the logic state of pin 9.
DTMF Decoder
The “touch tone” keys on a phone set generate Dual Tone Multi-Frequency (DTMF) tones. In a
POTS system, the DTMF tones are detected by the central ofice system, but in ISDN service, the
Terminal Adapter provides this function. The decoding inside the XEISDNP module converts the tones
to a digital signal the main ISDN controller (XEISDNU, for example) can read. It also generates a
DTMF_RDY signal to inform the controller a DTMF tone has been detected. The main controller then
issues a DTMF_EN signal to enable the DTMF code output to the system data bus. The four-bit DTMF
code is placed in the low byte of the data bus in the high nibble of the byte (D4 - D7).
Ring Signal Generation
An analog phone requires a 60_90VAC ring signal, so a voltage inverter has been designed inside
the module to convert the +12 volt power input into a high voltage ring supply output. Pin 3 is for
testing this voltage and should be bypassed to ground with a 10uF/250V capacitor. When DC_EN (pin
15) is pulled high by the TA Module, DC_OUT (pin 3) should have a 150_170 VDC output. The input
signal to control the ring active period is RING_EN (pin 14), which can be controlled by the TA Module
to cycle the ring signal (pin 2) in a pattern of two-seconds active or four-seconds active. (See Figure 1
on page 7)
Page 6
XEISDNP
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