Bell 202 modem, Bell 202T modem and ITU V.23 Specifications

Your ASE single-channel modem is a CMOS-based high performance modem offering full or half duplex 0-1200 bps asynchronous operation over leased line voice-grade circuits. It is fully compatible with Bell 202T modems, which means it fits perfectly into an existing network scheme without disturbing the network integrity. Since the unit has optional V.23 capabilities, it satisfies a wide range of domestic and international private-line applications.

Table 1 shows the FSK frequencies for the Bell 202/202T and the V.23 modems.

Modem Type	Mark Frequency (Logic 1)	Space Frequency (Logic 0)
Bell 202/202T	1200 Hz	2200 Hz
V.23	1300 Hz	2100 Hz

The ASE single-channel modem includes the following features:

900 Hz soft-carrier turnoff.
LED indicators for transmit data (TX), receive data (RX), request-to-send (RTS) clear-to-send (CTS), carrier detect (CD), and power.
DIP switches to select modem timing parameters (at one-millisecond increments).
Switch selectable transmit levels from 0 to –31dB.
Input power from +5 VDC.

The front view of the chassis with modems and power supplies, as well as the rear view for the location and description of the connectors.

Common Modem Settings

Transmit Output Level (JP7, SW1)

You can adjust the modem transmit output level two ways. One is a course setting of –16 dBm (via JP7), and the other is a fine tune setting of –1 dB increments (via SW1). JP7 allows you to decrease the modem output level by –16 dB, or keep the signal level at 0 dB (the default setting), as shown later. To decrease the output signal by –16 dB, remove the jumper at JP7.

SW1 (Switch 1)allows you to decrease the modem output transmit level in one decibel increments.

Receive Signal Jumper and Switch Settings.

Receive Carrier Detect Level Jumper (JP2)

You can set the required minimum receive carrier detect level that the modem uses before acknowledging that carrier is present. The default setting for the receive carrier detect is –35 dB.

Receive Squelch Jumper (JP3)

The modem chip has a jumper block (JP3) that sets the receive signal squelch. Install this jumper to provide 156 mS of receive squelch after completion of a transmission. This prevents the receiver inside the modem chip from seeing any signal. Use this jumper only when the modem is set up for 2-wire operation, or half duplex. In the default position, the modem chip immediately looks for the receive signal.

RTS to CTS Delay Switch (SW4)

The RTS to CTS delay enables the modem chip to bring up carrier for a specified amount of time before allowing transmit data to be sent out over the telephone line. SW4 sets the RTS/CTS timing delay. The RTS to CTS delay can be set from 0 to 254 milliseconds. The switch positions combine to equal the desired timing delay. For example, SW4 position 2 ON (2 mS) plus position 4 ON (8 mS) add up to 10 mS.

Receive Carrier Detect On Timing Delay Switch Settings (SW3)

The receive carrier detect on timing delay helps prevent the modem chip from generating spurious signals that cause false CD signals. The receive carrier detect on delay can be set from 2 to 30 milliseconds.

Other Jumper and Switch Settings

This section covers jumpers and switches that are not part of the Power Supply, Transmit, and Receive sections.

2-Wire / 4-Wire Select (JP4)

Your modem operates in two ways:

Two-wire mode for half duplex, with both the transmit and receive modem signals present on RJ11, pins 2 and 3
Four-wire mode for full duplex, with the transmit modem signal present on RJ11, pins 2 and 3, and the receive modem signal present on RJ11, pins 1 and 4

The factory default setting is the 4-wire configuration. For 4-wire mode, place the jumpers across JP4, pins 5, 6 and 7, 8. Place jumpers across JP4, pins 1, 2 and pins 3, 4 for 2-wire mode.

Constant Carrier (JP5)

The modem transmitter can be setup to provide a constant carrier signal if JP5 is installed. This jumper is normally installed if the modems are jumpered for four-wire, and are used in a point-to-point connection scheme (i.e. a master modem and a single stand alone modem).

RTS to CTS and DSR to DTR Jumper (JP1)

Some equipment connected to the ASE modem requires RTS to be jumpered to CTS, or DSR to be jumpered to DTR.

Jumper block JP1 allows you to jumper RTS to CTS and DSR to DTR. Below shows the jumper selections for JP1. If RTS to CTS or DSR to DTR connection is required, place jumper across pins 1 and 3 for RTS to CTS, and place jumper across pins 2 and 4 for DTR and DSR.

You may contact us in Campbell, CA by phone at 408-364-0500, fax to 408-364-0550, or via email at products@ase-systems.com.

Normal business hours are 9:00AM to 6:00PM Pacific Time, M - F.

Applied Systems Engineering, Inc.
1671 Dell Avenue, Suite 200
Campbell, California 95008
Phone: (408) 364-0500 • Fax: (408) 364-0550
Email: products@ase-systems.com

If you would like additional information on any of the ASE products or would like to discuss your specific requirements with a sales engineer, you can call directly or fax/e-mail the information about your requirement and a sales engineer will contact you.