Bell 208 A, Bell 208 B Modem - 208 A: Synchronous data transmission, full-duplex operation over 4-wire leased lines, half-duplex operation over 2-wire leased lines; 4800-bps data rate. 208 B: same as 208 A, but over 2-wire dialup lines. Comparable to ITU V.27. The first standards to enable higher-speed data transmission (4800 bps) over leased lines for multipoint, multidrop networks. For example, these standards enable us connect IBM mainframes at a central office to terminals in branch office, with fewer modems.

We stock used UDS 208A/B modems 208B/D modem 208C/D 208AB/AS

• 208A/B large version                              62085037

• 208A/B card long card version               62082066  

• 208A/B small "mini" case (RM16M)    62085064

• 208A/B RM16M card                             62085084

• 208A/BDC DC power                             6262085143

• 208B/D small "mini" case (RM16M)   6208096 or 6208097

• 208B/D RM16M card                            6208096 or 6208097

check out the other used modems at the bottom of the page

Reliable 4,800bps transmission over bad lines with 208A/B and 208 AB/AS (DPSK 8 phase) modem.
Multi-Point / Multi-Drop, Dial, 2 or 4 wire lease line.

UDS 208 SERIES 4800 bps The UDS 4800 series includes Bell 208 compatible modems which operate 4800 bps half duplex over 2-wire dial-up or leased lines. All models include automatic answer and line equalization, and all are compatible with the Universal Data Shelf". PRODUCT HIGHLIGHTS · 208A/B Operates full duplex over 4-wire leased lines; Includes antistreaming to prevent network tie-ups on multipoint networks · 208AB/AS Transmits asynchronous as well as synchronous data; Also operates full duplex over 4-wire leased lines; Includes antistreaming · 208B/D Includes synchronous automatic dialer which utilizes bisync protocol for DTE dialing communications; Features call progress monitoring for dial tone, busy signal, ring back and answer back tones

jump to UDS page

jump to PDF file of 208 A/B manual (5.5 megs)

Check out the DC powered modems jump to DC page

jump to new Racal Vadic / Zypcom 208A/B AC or DC powered modem

TECHNICAL DATA

 GENERAL SPECIFICATIONS          

• Data Rate                                4800 bps

• Modulation                              Eight-phase differentially coherent phase shift keying.

• Carrier Frequency                 1800 Hz

• Internal Transmit Clock       4800 Hz ± 0.0 1 % Frequency

• External Transmit Clock      4800 Hz ± 0.02 % Frequency

• Transmitter Output Level    0, -2, -4, -6, -8. -9, -10, -12 dBm and externally programmed.

• Line Impedance                     600 ohms, transformer coupled and transient  protected.

• Operation Mode                     2-wire, half-duplex PSTN or private line operation  and 4-wire full-duplex operation.

• Digital Interface                      Conforms to EIA Standards RS-232-C and CCITT V.24.

• Analog Interface                     FCC registered direct connect or leased line circuit.

• Clear to Send Delay              8.5 ms, 50 ms, or 150 ms

• Carrier Detect Range            0 to -34 dBm for private lines or 0 to -44 dBm for PSTN network.

• Line Equalizer                         Equalized for C2 conditioned lines or for 3002 unconditioned lines.

• Function Switch                     Rotary switch for Analog and Digital Loopback, Self Test, Transmit Test Pattern, Receive Test  Pattern, Data and Talk modes.  

THE MODEM POWER SUPPLY 

The standalone 208A/B modem unit contains a linear type power supply. All the power supply components are contained on the modem board except for the ac step down transformer. 

The maximum ac power input to the unit at a line voltage of 110 Vac is 10 watts. The maximum dc power used by the unit is 3.5 watts. 

THE MODEM TRANSMITTER 

The UDS 208 A/B transmitter is a 4800 bits per second synchronous quadrature modulated transmitter with a Bell 208A/B compatible data scrambler. The transmitter provides the option of a strap selectable fixed pre-equalizer to improve performance on poor quality phone lines. 

THE MODEM RECEIVER 

The UDS 208A/B receiver is a 4800 bit per second synchronous quadrature demodulator with a Bell compatible 208A/B descrambler. The receiver front-end contains an improved adaptive equalizer that provides for dynamic telephone line equalization. 

208A/B large version                              62085037
208A/B card long card version               62082066  
208A/B small "mini" case (RM16M)       62085064
208A/B RM16M card                            62085084

208A/BDC DC power                            6262085143

208B/D small "mini" case (RM16M)       6208096 or 6208097
208B/D RM16M card                           6208096 or 6208097
 

check out the
Racal Vadic / Zypcom
4800 bps HALF-DUPLEX (AT&T 208) MODEMS

VA4840-PX

RACKMOUNT AT&T 208 A/B compatible, Sync only, Up to 8 cards in a VA1681C chassis

(2 in VA1604). Dial-up or 2/4-wire leased line. Includes: modem, telco cable for dial-up and manual.

Note: 2-/4-wire leased line applications, order optional cable 15044-004.

4850PA

STANDALONE AT&T 208B and ITU-T V.27ter compatible, Sync only. Synchronous SADL

autodialer, front panel control w/LCD, Integral 801 ACU. Dial-up or 2-wire leased line. Includes: modem,

110V power supply, telco cable and manual, 801 ACU applications, order optional cable 91009-094.

jump to Racal Vadic page

Related Pages

• jump to Codex/Motorola Modems

• jump to UDS Modems

• jump to Multi-Drop Multi-Point modems

• jump to SCADA modems

• jump to VDC power modems

• jump to Industrial grade modems

• jump to Related modem pages   

• jump to SCADA CSU/DSU

• jump to other used modem pages
         

ARC ELECTRONICS
301-924-7400 EXT 25

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