External and Rackmount Bell 208 Modems

    • External 4850PA—Bell 208B, synchronous, half duplex, 4800 bps operation
    • Connects to 2-wire dial-up line, point-to-point
    • SADL (Synchronous Auto Dial Language), compatible with HDLC, SDLC and BSC protocols
    • Integral Bell 801ACU for RS366 dialing
    • LCD with full front-panel control, diagnostics and dialing
    • Rackmount 4840-PX—Bell 208A/B, synchronous, full or half duplex, 4800bps operation
    • Connects to 2-wire dial-up or 2-/4-wire leased lines, point-to-point or multi-point
    • 4840-PX mounts in 1681C or 1604 chassis
    • Accessories cards include: Bell 801ACU card and 831 asynchronous serial adapter card

    4850PA with Three Synchronous Protocols

    The 4850PA is not just another Bell 208 modem. This modem features an integral serial auto-dialer based on SADL (Synchronous Auto Dial Language). SADL dialing supports HDLC, SDLC and BSC protocols. SADL dialing eliminates the need for expensive RS366 computer ports and Bell 801 dialers. Whichever synchronous protocol you use, your system can issue dialing and options commands to the modem using SADL.

    Integral Bell 801 Dialer

    In addition to SADL, the 4850PA is compatible with the Bell 801 automatic calling unit parallel dialing protocol. With the 4850PA you do not have to purchase an external 801ACU because this modem has one built inside. Simply connect the optional 801ACU cable to your existing 801 dialer port.

    Flexible Operation

    You can operate the 4850PA from the terminal or the LCD front panel on the modem. Twenty-nine options let you customize the 4850PA to your application. No other Bell 208 modem comes close to the 4850PA in features, performance and price.

    Rackmount 4840-PX

    The 4840-PX delivers rock-solid performance for the high-density central site application. Each modem occupies two slots for a total of eight modems in the 16 slot 1681C chassis or a total of two modems in the 4 slot standalone desktop chassis.

    Package Deal

    Forty-eight 4840-PX modems will fit in a standard communications cabinet. The 4840-PX is compatible with two additional accessory cards, the 811D-PSR for RS366 dialing and the 831 adapter for parallel to serial conversion. The 4840-PX will operate with these accessory cards in either a single line or multiline configuration.

    They Never Rest

    When the modem is waiting to make a call or answer a call, the 4850PA and the 4840-PX run a continuous self-test that monitors each modem's transmitter, receiver, DSP and microprocessor for trouble. If a problem should occur, the modem can even take sick leave and remove itself from service.

    Small Wonders

    If you are looking for an external 208B or a rackmount 208A/B modem that is fast, powerful and heavy on features, we have the right one for you.


    4850PA and 4840-PX Modems

    4850PA: Bell 208B, V.27ter

    4840-PX: Bell 208A/B

    Operating Speeds 4800 bps

    4850PA: 2-wire dial-up, 2-wire leased line, half-duplex

    4840-PX: 2-wire dial-up, 2-/4-wire leased line, full or half-duplex, point-to-point or multi-point

    Data Format Synchronous: serial, binary

    DTE Interface EIA-232D, ITU-T V.24

    Transmit Levels

    Dial-up: -10 dBm permissive

    0 to -12 dBm programmable

    Leased line: 0 dBm


    Dial-up: -10 to -43 dBm

    0 to -12 dBm programmable

    Leased line: 0 dBm

    Receiver Sensitivity

    Dial-up: -10 to -43 dBm

    Leased line: 0 to -33 dBm


    Dial-up: -10 to -43 dBm

    Leased line: 0 to -33 dBm

    Training Time 50ms and 150ms

    Clock Timing Internal, external, or slave

    LCD/LED Display TXD, RXD, CTS, DSR, DTR, CXR, RI , Status

    Front Panel Keys
    4850PA: Redial, Dial, Display, Loop, Test, Reset, Data, Speed, Answer, Store #, Option, Enter

    4840-PX: ALB, RDLB, Transmit reversal

    Chassis Eight 4840-PX's will mount in the 1681C, two 4840-PX's will mount in the 1604

    Diagnostics Self-Test (ST), ALB, ALB-ST, RDLB, RDLB-ST

    4850PA: Height: 1.5"; width: 6.0"; length: 10.5"; weight: 1.5 lbs.

    4840-PX: Height: 6.0"; width: .5"; length: 12.7"; weight: 1.1 lbs.

    Power Requirements 110VAC—95 to 127VAC, 60Hz; 220VAC—190 to 250VAC, 50Hz

    Temperature Operating: 32°-122° F ambient; Store:-4°-158°F; Humidity:5-95%NC

    4850PA: FCC Part 68, Part 15_Class B

    4840-PX: FCC Part 68, Part 15_Class A

    4850PA Auto-Dialer

    Protocols SADL: HDLC, IBM-SDLC, IBM-BSC, Bell 801

    Dialer Type & Data Type: Tone, pulse, and automatic

    Data: Synchronous: serial, binary

    4840-PX Auto-Dialer (requires optional 811 and 831)

    Protocols Bell 801 and Vadic 831 language

    Dialer Type & Data Type: Tone, pulse, and automatic

    Bell 801data: Parallel RS366, binary

    Vadic 831: Asynchronous, serial, 10bit

    Ordering Information

    The 4850PA includes a permissive telephone cable with RJ11C connectors—P/N 15047-004. For 220VAC power supply, indicate after model number (ex. 4850PA, 220V). The 4840-PX takes up 2 slots in a chassis and includes a permissive telephone cable with RJ11C connector—P/N 15027-004.

    Models Description

    4850PA External Bell 208B modem

    4840-PX Rackmount Bell 208A/B modem


    15044-004 4840-PX 4-wire leased line cable

    15022-004 4840-PX 2-wire leased line cable

    91009-094 4850PA Bell 801 Y-cable

    1681C Sixteen slot chassis for 4840-PX

    1604 Four slot chassis for 4840-PX

    811 Bell 801 rackmount dialer (RS366)

    831 Adapter RS366 to RS232


29400 Kohoutek Way, Suite 170
Union City, CA 94587-1212
Tel: 510-324-2501 Fax: 510-324-2414